Hi all! I have a little program (written in VB6) that saves the image in 
a picturebox to a BMP file. The problem is that BMP files are several 
megabytes in size and do not support DPI (dots-per-inch) information for 
printing.

I have turned to the PNG format which provides lossless compression 
(files are only few kilobytes) and includes DPI information.

But how do I save the image in a picturebox to a PNG file?

Thanks in advance!

"Nando" <hightech@att.net.no.to.sp.am> wrote in message 
news:uflaC5aMLHA.2100@TK2MSFTNGP06.phx.gbl...

> Hi all! I have a little program (written in VB6) that saves the
> image in a picturebox to a BMP file. The problem is that BMP
> files are several megabytes in size and do not support DPI
> (dots-per-inch) information for printing. I have turned to the
> PNG format which provides lossless compression (files are
> only few kilobytes) and includes DPI information.

The png format will give you those kind of lossless compressions (50:1 or 
even more) on simple images, such as line drawings with filled sections and 
graphs and other images with a limited number of colours and many small or 
large areas of a solid colour, but the png lossless compression of a tpyical 
photo will be much less, perhaps in the order of 2:1 or something of that 
nature. So, if your images are of the kind I first mentioned then png is 
definitely one way to go if you want high compression, but if they are 
typical photos (and if compression is your main concern) then the lossy but 
still quite good compression of a jpg might be more suitable (although the 
fact that png can give you lossless compression on photos might be exactly 
what you want if compression is not your main concern). As far as DPI 
information in an image file is concerned, that's a moot point that I won't 
go into here because I sometimes get into lots of trouble from various 
people for writing too much waffle :-)

> But how do I save the image in a picturebox to a PNG file?

I reckon GDI+ is probably your best bet. Have a look at:

http://www.vbaccelerator.com/home/vb/code/vbmedia/using_gdi_plus/Reading_and_Writing_JPG__PNG__TIF_and_GIF_Files/article.asp

Mike

"Nando" <hightech@att.net.no.to.sp.am> wrote in message 
news:uflaC5aMLHA.2100@TK2MSFTNGP06.phx.gbl...
> Hi all! I have a little program (written in VB6) that saves the image in a 
> picturebox to a BMP file. The problem is that BMP files are several 
> megabytes in size and do not support DPI (dots-per-inch) information for 
> printing.
>
> I have turned to the PNG format which provides lossless compression (files 
> are only few kilobytes) and includes DPI information.
>
> But how do I save the image in a picturebox to a PNG file?


VB6 does not natively support the PNG format. Look for an OCX or DLL that 
does (sorry, I personally don't know of any or I'd suggest one).  Or, I 
suppose you could search the Internet for the PNG format's file spec and 
write the file yourself. Finding an OCX/DLL would probably be a lot easier, 
and I'd be willing to bet there are free ones out there that shouldn't be 
too hard to find.

-- 
Mike

 

Nando...

There are plenty of free resources out there for saving an image in
the PNG format.

One is the Free Image open source DLL.  It even has VB6 examples.
It's open source and available at:

http://freeimage.sourceforge.net/sourcecode.html

Even Microsoft provides that ability with the Windows Image
Acquisition Library (WIA) found here:

http://www.microsoft.com/downloads/details.aspx?displaylang=en&FamilyID=a332a77a-01b8-4de6-91c2-b7ea32537e29

Mike Williams also gave you a good resource at vbAcclerator.

And, btw, Mike.... one man's waffle is another man's treasure.  I
usually learn something with your "waffles".  Don't stop now!

Tom

> And, btw, Mike.... one man's waffle is another man's treasure.  I
> usually learn something with your "waffles".  Don't stop now!

what I would like to underwrite, too!

"Shotgun Thom" <tmoran4511@gmail.com> skrev i meddelelsen 
news:ec98930c-1768-4419-8b51-2ab6a77baaa7@t5g2000prd.googlegroups.com...
> Nando...
>
> There are plenty of free resources out there for saving an image in
> the PNG format.
>
> One is the Free Image open source DLL.  It even has VB6 examples.
> It's open source and available at:
>
> http://freeimage.sourceforge.net/sourcecode.html
>
> Even Microsoft provides that ability with the Windows Image
> Acquisition Library (WIA) found here:
>
> http://www.microsoft.com/downloads/details.aspx?displaylang=en&FamilyID=a332a77a-01b8-4de6-91c2-b7ea32537e29
>
> Mike Williams also gave you a good resource at vbAcclerator.
>
> And, btw, Mike.... one man's waffle is another man's treasure.  I
> usually learn something with your "waffles".  Don't stop now!
>
> Tom
>

It constitutes a long chain to trace back:

    * From: "senn" <senn@homeplace&.fix>
    * Date: Sun, 18 May 2008 19:34:26 +0200

"Mike Williams" <mikea@xxxxxxxxxxxxxxxxx> skrev i en meddelelse
news:ucj7kpPuIHA.3968@xxxxxxxxxxxxxxxxxxxxxxx

    Okay, Senn. I'll give it a whirl later. What do I need to download and
    install in order to make it work? Can you post a link?

    Mike


GDI+ TypeLib TLB
-Unicode Logo
Generator
http://www.planet-source-code.com/upload_PSC/ftp/GDI+_TypeL154059272003.zip

/senn

And Karls answer to this back then:

None of that nonsense. And, even if you're stuck using that other lib, you 
can
still use FreeImage_GetFileType to tell you what sort of file you're dealing 
with.
:-)
-- 
...NET: It's About Trust!

http://vfred.mvps.org

/se 

senn wrote:
>
> GDI+ TypeLib TLB
> -Unicode Logo
> Generator
> http://www.planet-source-code.com/upload_PSC/ftp/GDI+_TypeL154059272003.zip
>
> /senn
>
> And Karls answer to this back then:
>
> None of that nonsense. And, even if you're stuck using that other lib,
> you can
> still use FreeImage_GetFileType to tell you what sort of file you're
> dealing with.
> :-)

Hi guys! I must share that I spent a great deal of time yesterday and 
today understanding and implementing the GDI+ TypeLib routines within my 
app. I just couldn't resist the temptation of having more than one file 
type to save to (I only needed .PNG but I got greedy). GDI+ seemed to 
offer so many other file types. Unfortunately after so much work and 
troubleshooting I found I can only generate 32-bit transparent PNG files 
and never 24-bit ones (just the very ones I need, since the 24-bit PNGs 
do not support transparency and I cannot have transparency :-( Oh 
well... can somebody just confirm this? Thanks!

-Nando

P.S.: Seems like the parameter "EncoderColorDepth" can only be set for 
..JPG and .TIF. Seems like the GDI+ PNG codec just ignore any parameter.

Shotgun Thom wrote:
 >
> There are plenty of free resources out there for saving an image in
> the PNG format.
>
> One is the Free Image open source DLL.  It even has VB6 examples.
> It's open source and available at:
>
> http://freeimage.sourceforge.net/sourcecode.html

That is great Tom! I'll definetly look into that free image library. I 
like the fact that you say they have VB6 examples! Awesome!

> Even Microsoft provides that ability with the Windows Image
> Acquisition Library (WIA) found here:
>
> http://www.microsoft.com/downloads/details.aspx?displaylang=en&FamilyID=a332a77a-01b8-4de6-91c2-b7ea32537e29

Interesting, I would like to try that (WIA Lib). Although I'm quite 
scare now, since I spent too much time already with another Microsoft 
library (GDI+) just to find out that it does not really do what I 
wanted. I'll look into WIA Lib, but with reserves.

I'm not doing too much image manipulation in my app, just need to save a 
bitmap file to a 24-bit PNG file. I also needed to read the bitmap and 
create a new one setting DPI and resize it using basic 
"Nearest-Neighbor" interpolation. I had all that figured out and set up 
in my app using GDI+ (which until yesterday I never worked with). Now I 
have to start from scratch. Hopefully the Free Image Library will be 
more helpful.

-Nando

Hi Nando...

An even easier solution is to add the code included in this post to
your project in a Module:

It allows you to save your Picture Box as a 24bit PNG, JPG or BMP.

Once you have the picture displayed in your picture box you just call
the Sub as follows:

SaveImageAs "c:\mypicture.png", Picture1.hdc,  Picture1.Width /
Screen.TwipsPerPixelX,  Picture1.Height / Screen.TwipsPerPixelY,
CLng(100)

Open a new module in your project.  Copy the following code and paste
into the module.  Use the syntax above to call saving the image,
replacing, obviously, the file name with your own and with whatever
you named your Picture Box.

Option Explicit
'///////////////////////////////////////////////////
'// SaveImageAs - Save hDC to Bitmap or Jpeg file //
'// Ed Wilk/Edgemeal - last updated Feb.06,2010   //
'///////////////////////////////////////////////////

Private Const BI_RGB As Long = 0
Private Const DIB_RGB_COLORS As Long = 0

Private Type BitmapFileHeader
    bfType As Integer
    bfSize As Long
    bfReserved1 As Integer
    bfReserved2 As Integer
    bfOffBits As Long
End Type

Private Type BitmapInfoHeader
  biSize As Long
  biWidth As Long
  biHeight As Long
  biPlanes As Integer
  biBitCount As Integer
  biCompression As Long
  biDataSize As Long
  biXPelsPerMeter As Long
  biYPelsPerMeter As Long
  biClrUsed As Long
  biClrImportant As Long
End Type

Private Type RGBQUAD
  rgbBlue As Byte
  rgbGreen As Byte
  rgbRed As Byte
  rgbReserved As Byte
End Type

Private Type BITMAPINFO
  bmiHeader As BitmapInfoHeader
  bmiColors As RGBQUAD
End Type

Private Declare Function DeleteDC Lib "gdi32" (ByVal hdc As Long) As
Long
Private Declare Function DeleteObject Lib "gdi32" (ByVal hObject As
Long) As Long
Private Declare Function CreateCompatibleDC Lib "gdi32" (ByVal hdc As
Long) As Long
Private Declare Function SelectObject Lib "gdi32" (ByVal hdc As Long,
ByVal hObject As Long) As Long
Private Declare Function CreateDIBSection Lib "gdi32" (ByVal hdc As
Long, pBitmapInfo As BITMAPINFO, ByVal un As Long, ByVal lplpVoid As
Long, ByVal handle As Long, ByVal dw As Long) As Long
Private Declare Function GetDIBits Lib "gdi32" (ByVal aHDC As Long,
ByVal hBitmap As Long, ByVal nStartScan As Long, ByVal nNumScans As
Long, lpBits As Any, lpBI As BITMAPINFO, ByVal wUsage As Long) As Long
Private Declare Function BitBlt Lib "gdi32" (ByVal hDestDC As Long,
ByVal X As Long, ByVal Y As Long, ByVal nWidth As Long, ByVal nHeight
As Long, ByVal hSrcDC As Long, ByVal xSrc As Long, ByVal ySrc As Long,
ByVal dwRop As Long) As Long

' gdi+
Private Type GUID
   Data1 As Long
   Data2 As Integer
   Data3 As Integer
   Data4(0 To 7) As Byte
End Type

Private Type GdiplusStartupInput
   GdiplusVersion As Long
   DebugEventCallback As Long
   SuppressBackgroundThread As Long
   SuppressExternalCodecs As Long
End Type

Private Type EncoderParameter
   GUID As GUID
   NumberOfValues As Long
   Type As Long
   Value As Long
End Type

Private Type EncoderParameters
   Count As Long
   Parameter As EncoderParameter
End Type

Private Declare Function GdiplusStartup Lib "GDIPlus" ( _
   token As Long, _
   inputbuf As GdiplusStartupInput, _
   Optional ByVal outputbuf As Long = 0) As Long

Private Declare Function GdiplusShutdown Lib "GDIPlus" ( _
   ByVal token As Long) As Long

Private Declare Function GdipCreateBitmapFromHBITMAP Lib "GDIPlus" ( _
   ByVal hbm As Long, _
   ByVal hPal As Long, _
   Bitmap As Long) As Long

Private Declare Function GdipDisposeImage Lib "GDIPlus" ( _
   ByVal Image As Long) As Long

Private Declare Function GdipSaveImageToFile Lib "GDIPlus" ( _
   ByVal Image As Long, _
   ByVal Filename As Long, _
   clsidEncoder As GUID, _
   encoderParams As Any) As Long

Private Declare Function CLSIDFromString Lib "ole32" ( _
   ByVal str As Long, _
   id As GUID) As Long




Public Sub SaveImageAs(ByVal sFileName As String, ByVal Source_hDC As
Long, ByVal Width As Long, ByVal Height As Long, Optional ByVal
Quality As Long = 80)
    Dim sFileExt As String
    Dim myDIB As Long, myDC As Long, fNum As Long
    Dim bi24BitInfo As BITMAPINFO
    Dim fileheader As BitmapFileHeader
    Dim bitmapData() As Byte
    ' gdi
    Dim tSI As GdiplusStartupInput
    Dim lRes As Long, lGDIP As Long, lBitmap As Long
    Dim tJpgEncoder As GUID
    Dim tParams As EncoderParameters

    ' source hDC to DIB
    With bi24BitInfo.bmiHeader
      .biBitCount = 24
      .biCompression = BI_RGB
      .biPlanes = 1
      .biSize = Len(bi24BitInfo.bmiHeader)
      .biWidth = Width
      .biHeight = Height
      .biDataSize = ((.biWidth * 3 + 3) And &HFFFFFFFC) * .biHeight
      ReDim bitmapData(0 To .biDataSize - 1)
    End With
    myDC = CreateCompatibleDC(0)
    myDIB = CreateDIBSection(myDC, bi24BitInfo, DIB_RGB_COLORS, ByVal
0&, ByVal 0&, ByVal 0&)
    SelectObject myDC, myDIB
    BitBlt myDC, 0, 0, bi24BitInfo.bmiHeader.biWidth,
bi24BitInfo.bmiHeader.biHeight, Source_hDC, 0, 0, vbSrcCopy
    Call GetDIBits(myDC, myDIB, 0, bi24BitInfo.bmiHeader.biHeight,
bitmapData(0), bi24BitInfo, DIB_RGB_COLORS)

    ' get file extension of filename to save as lower case.
    sFileExt = LCase$(GetFileExt(sFileName))
    ' Save image to file....
    Select Case sFileExt
        Case ".bmp"   ' save as bmp....
            With fileheader
                .bfType = &H4D42
                .bfOffBits = Len(fileheader) +
Len(bi24BitInfo.bmiHeader)
                .bfSize = bi24BitInfo.bmiHeader.biDataSize
+ .bfOffBits
            End With
            fNum = FreeFile
            On Error GoTo BadFileName
            Open sFileName For Output As fNum
            Close fNum
            Open sFileName For Binary As fNum
            Put fNum, , fileheader
            Put fNum, , bi24BitInfo.bmiHeader
            Put fNum, , bitmapData()
            Close fNum
        Case ".jpg", ".png"
            tSI.GdiplusVersion = 1 ' Initialize GDI+
            lRes = GdiplusStartup(lGDIP, tSI)
            If lRes = 0 Then
                lRes = GdipCreateBitmapFromHBITMAP(myDIB, 0, lBitmap)
' Create the GDI+ bitmap from the image handle
                If lRes = 0 Then
                    If sFileExt = ".jpg" Then ' JPG
                        CLSIDFromString
StrPtr("{557CF401-1A04-11D3-9A73-0000F81EF32E}"), tJpgEncoder
                        ' Initialize the encoder parameters
                        tParams.Count = 1
                        With tParams.Parameter ' jpeg Quality
                          CLSIDFromString StrPtr("{1D5BE4B5-
FA4A-452D-9CDD-5DB35105E7EB}"), .GUID
                          .NumberOfValues = 1
                          .Type = 4
                          .Value = VarPtr(Quality)
                        End With
                    ElseIf sFileExt = ".png" Then ' PNG
                        CLSIDFromString
StrPtr("{557CF406-1A04-11D3-9A73-0000F81EF32E}"), tJpgEncoder
                    End If
                    ' Save the image
                    lRes = GdipSaveImageToFile(lBitmap,
StrPtr(sFileName), tJpgEncoder, tParams)
                    ' Destroy the bitmap
                    GdipDisposeImage lBitmap
                End If
              ' Shutdown GDI+
              GdiplusShutdown lGDIP
            End If
            If lRes Then
                Err.Raise 5, , "Can not save image(GDI+ Error).:" &
lRes
            End If
    End Select
Fini:
    DeleteObject myDIB
    DeleteDC myDC
    Exit Sub

BadFileName:
    Close fNum
    Err.Raise 5, , "Can not save BMP image.:" & lRes
    Resume Fini
End Sub
Private Function GetFileExt(sFile As String) As String
    ' example" returns ".exe"
    Dim I As Integer
    I = InStrRev(sFile, ".")
    If I Then
        GetFileExt = Mid$(sFile, I)
    Else
        GetFileExt = sFile ' if not found then just return the whole
string
    End If
End Function



Thanks to Ed Wilk for this code I downloaded from somewhere but can't
remember.

Tom

Shotgun Thom wrote:
> Hi Nando...
>
> An even easier solution is to add the code included in this post to
> your project in a Module:
>
> It allows you to save your Picture Box as a 24bit PNG, JPG or BMP.
>
> Once you have the picture displayed in your picture box you just call
> the Sub as follows:
>
> SaveImageAs "c:\mypicture.png", Picture1.hdc,  Picture1.Width /
> Screen.TwipsPerPixelX,  Picture1.Height / Screen.TwipsPerPixelY,
> CLng(100)
>
> Open a new module in your project.  Copy the following code and paste
> into the module.  Use the syntax above to call saving the image,
> replacing, obviously, the file name with your own and with whatever
> you named your Picture Box.
>
><Snipped>
>
> Thanks to Ed Wilk for this code I downloaded from somewhere but can't
> remember.
>
> Tom

Thanks a billion Tom!!! I'm now able to create 24-bit PNG files!!!

I'm multitasking a lot of stuff on my side, but one thing I'm still 
experiment (just for curiosity) is why (for a specific BMP image sample) 
I get different file sizes of 18KB and 23KB.

The sample image: A snapshot of the calculator of Windows XP as a BMP 
file (446KB).

The PNG version of the file is 23KB (using the API code). I also get the 
same result if I save the file manually as a PNG from MS Paint.

However, I get a smaller PNG version of 18KB saving the sample file as 
PNG using Microsoft Photo Editor 3 (which shipped with Office XP or 
2003). This was a smaller size without any loss in quality since I 
checked by re-saving the PNG as a BMP and comparing with the sample, and 
they matched bit by bit (SourceForge's WinMerge).

Just wondering how Photo Editor was able to produce a file 78% smaller 
under the same PNG format. The quality specified using the API was set 
to 100, so I'm quite intrigued.

-Nando

First of all, the Quality Setting included in the code I posted is
only applied when saving a file as a JPEG.  75 is a reasonable setting
for quality of a JPEG image that's purpose is to be viewed on a
monitor.  Good compression and reasonable quality.  Get much lower
than that and you may begin to notice the image deterioration.

Regarding the PNG file size differences... it all has to do with
compression techniques.  There are a bunch of tool/utilities
(PngCrush, PNGOUT, etc.) out there that do nothing but compress
existing PNG files.  There's even an online site  (www.punypng.com)
where you upload your PNG and it will reduce it for you and send it
back.  Google PNG Compression Tools and you'll see the plethora of
choices.

The nice thing about all these compression tools is there, usually, is
no loss of image quality.  The API code uses a pretty standard png
saving format.  Other utilities/programs, obviously, have tweaked the
compression.  Kinda like the difference between WinZip, GZip and 7Zip
compression.  They are all Zip tools... just different compression.

Tom

Shotgun Thom wrote:
> Regarding the PNG file size differences... it all has to do with
> compression techniques.  There are a bunch of tool/utilities
> (PngCrush, PNGOUT, etc.) out there that do nothing but compress
> existing PNG files.  There's even an online site  (www.punypng.com)
> where you upload your PNG and it will reduce it for you and send it
> back.  Google PNG Compression Tools and you'll see the plethora of
> choices.
>
> The nice thing about all these compression tools is there, usually, is
> no loss of image quality.  The API code uses a pretty standard png
> saving format.  Other utilities/programs, obviously, have tweaked the
> compression.  Kinda like the difference between WinZip, GZip and 7Zip
> compression.  They are all Zip tools... just different compression.

Very interesting stuff Tom! Great site too (punypng.com).

I'm not planning to work on this, but I must sort my curiosity here :-) 
I'm not an expert in file formats, my understanding is based mostly in 
the common idea that an electronic image is just that, a 3D matrix of 
dots (x, y, color) with that info as part of the file's header.

However, if there are so many tools around that offer different 
types/levels of lossless compressions (and the files are still 
backward-compatible for displaying in browsers and old editors) then 
that implies these tools must be injecting the PNG file with the 
*actual* code/algorithm that decompresses the picture. Which leads me to 
the idea of a security vulnerability (right?). I'm not getting paranoid, 
only curious. Is this the way PNG images are crafted?

Nando wrote:
>
> I'm not planning to work on this, but I must sort my curiosity here :-)
> I'm not an expert in file formats, my understanding is based mostly in
> the common idea that an electronic image is just that, a 3D matrix of
> dots (x, y, color) with that info as part of the file's header.
>

Many image formats also have the capacity to store metadata, so that the 
image is self describing - useful for archiving purposes.

http://www.steelbytes.com/?mid=30
for example, can strip such information from png/jpg files.

Perhaps the software you are using is also stripping that information - 
because there is no standard way of adding such data to PNG files.

A couple of side notes that might be useful:

* I'm not certain, but I think WIA is XP-only.

* If you look at planetsourcecode for Peter
Scale you'll find sample projects that provide
straight VB code for many graphic operations,
including not only "nearest neighbor" bilinear
resizing but also bicubic. (Though if I remember
correctly, starting with XP a basic StretchBLT
can use bicubic.)


| Interesting, I would like to try that (WIA Lib). Although I'm quite
| scare now, since I spent too much time already with another Microsoft
| library (GDI+) just to find out that it does not really do what I
| wanted. I'll look into WIA Lib, but with reserves.
|

| I'm not doing too much image manipulation in my app, just need to save a
| bitmap file to a 24-bit PNG file. I also needed to read the bitmap and
| create a new one setting DPI and resize it using basic
| "Nearest-Neighbor" interpolation. I had all that figured out and set up
| in my app using GDI+ (which until yesterday I never worked with). Now I
| have to start from scratch. Hopefully the Free Image Library will be
| more helpful.
|
| -Nando 

Hi Nano...

Jason is correct in that most image formats can store metadata (EXIF)
information in the image.  Here's an example of such informaion from a
typical .PNG:

File Name                       : balloonhotair.png
Directory                         : C:/iPic
File Size                         : 1571 kB
File Modification Date/Time     : 2010:08:13 13:35:28-07:00
File Permissions              : rw-rw-rw-
File Type                         : PNG
MIME Type                      : image/png
Image Width                    : 1024
Image Height                   : 768
Bit Depth                         : 8
Color Type                       : RGB
Compression                   : Deflate/Inflate
Filter                               : Adaptive
Interlace                          : Noninterlaced
SRGB Rendering              : Perceptual
Gamma                           : 2.2
White Point X                   : 0.3127
White Point Y                   : 0.329
Red X                               : 0.64
Red Y                               : 0.33
Green X                             : 0.3
Green Y                            : 0.6
Blue X                               : 0.15
Blue Y                              : 0.06
Modify Date                      : 2002:10:07 10:06:47
Description                     :
Creation Time                   : 2002:10:05 07:34:53
Software                          : iQ ImageXpress
Source                            : CYBERSHOT
Image Size                      : 1024x768

This data is easily modified or can be deleted from virtually any PNG
image.  I'm sure that would give some kind of size saving... just not
sure how much.

As far as security, I'm not sure what type of security, or
paranoia :) , you mean.  Some photographers put copyright information
as part of image metadata so that could be tampered with.

Regarding Mayayana's post

A couple of side notes that might be useful:

> I'm not certain, but I think WIA is XP-only.

I think that is correct.  While Win 7 has wiautt.dll pre-installed I
don't believe it's the same version 2.0.  I know I tried using the
Printing features of WIA Ver 2.0 on Win 7 and it crapped out.



Tom

Jason Keats wrote:

> Many image formats also have the capacity to store metadata, so that the
> image is self describing - useful for archiving purposes.
>
> http://www.steelbytes.com/?mid=30
> for example, can strip such information from png/jpg files.

Nice tool!

> Perhaps the software you are using is also stripping that information -
> because there is no standard way of adding such data to PNG files.

Definetly out of topic question now: is there a similar tool to for 
optimizing or cleaning/removing junk from a VB6 EXE file?

Shotgun Thom wrote:

> As far as security, I'm not sure what type of security, or
> paranoia :) , you mean.  Some photographers put copyright information
> as part of image metadata so that could be tampered with.

My suspicion was that PNG files (in addition to the image data itself) 
would have the actual decompression code/engine embedded into the file. 
Hope my assumption is incorrect. Images should behave as a static data 
file that is read by the browser and not as an EXE that provides the 
browser the "execution" code to allow access to re-construct the image data.

I arrived to that conclusion to explain the fact that (with so many new 
compression tools creating different PNG level of compressions) newly 
created PNG files get actually understood/displayed/rendered by old 
graphic software and browsers. That is a trait of a fixed image format.

"Nando" <hightech@att.net.no.to.sp.am> wrote in message 
news:O3R7de1OLHA.2100@TK2MSFTNGP02.phx.gbl...

> My suspicion was that PNG files (in addition to the image
> data itself) would have the actual decompression code/engine
> embedded into the file. Hope my assumption is incorrect.

    http://www.libpng.org/pub/png/

Mike

"Nando" <hightech@att.net.no.to.sp.am> wrote in message 
news:O3R7de1OLHA.2100@TK2MSFTNGP02.phx.gbl...

> My suspicion was that PNG files (in addition to the image
> data itself) would have the actual decompression code/engine
> embedded into the file.

I very much doubt it, although I think that the PNG file does contain 
certain flags that can instruct the actual decompression engine to modify 
its behaviour in certain ways.

> I arrived to that conclusion to explain the fact that (with so
> many new compression tools creating different PNG level
> of compressions) newly created PNG files get actually
> understood/displayed/rendered by old graphic software
> and browsers.

To be perfectly honest I don't know anything at all about the details of the 
PNG image format but according to various bits of information on the web 
page to which I recently posted a link it would appear that the format 
contains a number of things which would allow different applications to 
achieve different levels of compression. I was particularly interested in 
the fact that the format compresses each horizontal scanline separately, and 
that there are five standard compression filters available, each of which is 
best suited for compressing specific kinds of scanline image data. 
Apparently a different compression filter (one of the five available) can be 
applied to each individual scanline (the filter number is obviously included 
in the compressed data for each line). This means that by analyzing the 
image data line by line and intelligently choosing which of the five 
available filters is best suited to each specific horizontal line of a 
bitmap, an application can achieve greater compression than some other 
application that either uses a single filter throughout or that does not 
choose the filters intelligently. I think that is probably one of the main 
reasons why certain applications are better at producing lower file size 
PNGs than others, although it seems to be a fairly complicated format and 
there are probably others.

Mike

 

Nando wrote:
> Definetly out of topic question now: is there a similar tool to for
> optimizing or cleaning/removing junk from a VB6 EXE file?

No.

However, there are tools to remove dead code from your source - so that 
it doesn't get compiled into your exe in the first place.
http://www.mztools.com/v3/mztools3.aspx

Some can do much more than that, like static code analysis to find 
problems and even duplicate code.
http://www.aivosto.com/project/project.html

There are tools to replace all strings in your code with a function 
lookup - to remove duplicate text and prepare your program for 
translation of the GUI.
http://www.resourcemining.com/ResMe.htm

You can also compress your exe, if you wish.
http://upx.sourceforge.net/

"Jason Keats" <jkeats@melbpcDeleteThis.org.au> wrote in message 
news:a5u9o.3569$Yv.1378@viwinnwfe01.internal.bigpond.com...
> However, there are tools to remove dead code from your source - so that it 
> doesn't get compiled into your exe in the first place.
> http://www.mztools.com/v3/mztools3.aspx

I found that VB6 compiler removes functions that are not being called 
anywhere, except if the function is Public in an object model(Form, Class, 
UserControl), because it's Public functions are part of the interface for 
these objects. If the function was private, it would be removed. Public or 
Private functions that are not being called anywhere in a BAS module are 
removed.

How do I know this? I viewed the disassembly in VC6 for a test program. This 
is known as function-level linking, and I am glad that VB uses it.

Nobody wrote:
> "Jason Keats"<jkeats@melbpcDeleteThis.org.au>  wrote in message
> news:a5u9o.3569$Yv.1378@viwinnwfe01.internal.bigpond.com...
>> However, there are tools to remove dead code from your source - so that it
>> doesn't get compiled into your exe in the first place.
>> http://www.mztools.com/v3/mztools3.aspx
>
> I found that VB6 compiler removes functions that are not being called
> anywhere, except if the function is Public in an object model(Form, Class,
> UserControl), because it's Public functions are part of the interface for
> these objects. If the function was private, it would be removed. Public or
> Private functions that are not being called anywhere in a BAS module are
> removed.
>
> How do I know this? I viewed the disassembly in VC6 for a test program. This
> is known as function-level linking, and I am glad that VB uses it.
>

Thanks, I'm glad to hear the VB compiler is (somewhat) smarter than I 
thought.

However, I still think it's worthwhile to occasionally check for dead 
code. There is usually a surprising amount of "junk code" in most 
people's work after a while - removing unused routines and declaration 
can be helpful.

Jason Keats wrote:
> Nando wrote:
>> Definetly out of topic question now: is there a similar tool to for
>> optimizing or cleaning/removing junk from a VB6 EXE file?
>
> No.
>
> However, there are tools to remove dead code from your source - so that
> it doesn't get compiled into your exe in the first place.
> http://www.mztools.com/v3/mztools3.aspx

Thanks Jason!

> Some can do much more than that, like static code analysis to find
> problems and even duplicate code.
> http://www.aivosto.com/project/project.html

Cool!!

> There are tools to replace all strings in your code with a function
> lookup - to remove duplicate text and prepare your program for
> translation of the GUI.
> http://www.resourcemining.com/ResMe.htm
>
> You can also compress your exe, if you wish.
> http://upx.sourceforge.net/

Nobody wrote:

> I found that VB6 compiler removes functions that are not being called
> anywhere, except if the function is Public in an object model(Form, Class,
> UserControl), because it's Public functions are part of the interface for
> these objects. If the function was private, it would be removed. Public or
> Private functions that are not being called anywhere in a BAS module are
> removed.
>
> How do I know this? I viewed the disassembly in VC6 for a test program. This
> is known as function-level linking, and I am glad that VB uses it.

Nice finding Nobody! I'll keep it in mind when coding.

Mike Williams wrote:
> Nando wrote:
>
>> My suspicion was that PNG files (in addition to the image
>> data itself) would have the actual decompression code/engine
>> embedded into the file.
>
> I very much doubt it, although I think that the PNG file does contain
> certain flags that can instruct the actual decompression engine to
> modify its behaviour in certain ways.

Interesting

>> I arrived to that conclusion to explain the fact that (with so
>> many new compression tools creating different PNG level
>> of compressions) newly created PNG files get actually
>> understood/displayed/rendered by old graphic software
>> and browsers.
>
> To be perfectly honest I don't know anything at all about the details of
> the PNG image format but according to various bits of information on the
> web page to which I recently posted a link it would appear that the
> format contains a number of things which would allow different
> applications to achieve different levels of compression. I was
> particularly interested in the fact that the format compresses each
> horizontal scanline separately, and that there are five standard
> compression filters available, each of which is best suited for
> compressing specific kinds of scanline image data. Apparently a
> different compression filter (one of the five available) can be applied
> to each individual scanline (the filter number is obviously included in
> the compressed data for each line). This means that by analyzing the
> image data line by line and intelligently choosing which of the five
> available filters is best suited to each specific horizontal line of a
> bitmap, an application can achieve greater compression than some other
> application that either uses a single filter throughout or that does not
> choose the filters intelligently. I think that is probably one of the
> main reasons why certain applications are better at producing lower file
> size PNGs than others, although it seems to be a fairly complicated
> format and there are probably others.
>
> Mike

The format does seem quite complex and advanced. That would definitely 
explains the different PNG sizes, compression levels without being tied 
up to a single format-version or compression format. No wonder it is the 
World Wide Web Consortium (W3C)'s standard :)

Thanks a lot Mike! That solves the mystery. Hope there isn't any file 
format out-there implementing my wild thought of embedding decompression 
engines ;)

Mike Williams wrote:
> Nando wrote:
>> My suspicion was that PNG files (in addition to the image
>> data itself) would have the actual decompression code/engine
>> embedded into the file. Hope my assumption is incorrect.
>
> http://www.libpng.org/pub/png/
>
> Mike

Oh boy! So I wasn't so off after all. I was fast-reading the PNG 
specification document and I was shocked after finding this:

"A PNG file or datastream is composed of a collection of explicitly 
typed "chunks". Chunks whose contents are defined by the specification 
could actually contain anything, including malicious code. But there is 
no known risk that such malicious code could be executed on the 
recipient�s computer as a result of decoding the PNG image. The possible 
security risks associated with future chunk types cannot be specified at 
this time." (section 5, pg 33, pgph 2-3)

Reference:
<http://www.libpng.org/pub/png/spec/1.0/png-1.0.pdf>

"Nando" <hightech@att.net.no.to.sp.am> wrote in message 
news:eCr94$CPLHA.5644@TK2MSFTNGP04.phx.gbl...

 > Oh boy! So I wasn't so off after all. I was fast-reading
> the PNG specification document and I was shocked
> after finding this: "A PNG file or datastream is composed of a collection 
> of
> explicitly typed "chunks". Chunks whose contents are defined
> by the specification could actually contain anything, including
> malicious code. But there is no known risk that such malicious
> code could be executed on the recipient�s computer as a result
> of decoding the PNG image. The possible security risks
> associated with future chunk types cannot be specified at this time." 
> (section 5, pg 33, pgph 2-3)

Well I don't think that's a problem specific to PNG files. Malicious code 
can be contained inside almost any data file. Any code, including malicious 
code, is just a bunch of numbers, in the same way that image data (for 
example) is just a bunch of numbers. The hard part (from a trojan writer's 
point of view!) is in getting that code to run. I don't actually know 
anything at all about writing trojans, but I seem to recall reading that in 
certain circumstances it is possible to do get contained data to run as code 
by arranging the data in such a way that a legitimate application which is 
reading the file gets "tricked" by certain blocks of data not being quite 
what it was expecting, causing the application to overwrite the area of 
memory it had been allocated for writing into and causing a buffer overflow. 
I think it is sometimes possible to craft the data in such a way that the 
processor ends up executing code at an address supplied by the data on 
return from the error. Something like that, anyway. I don't think what you 
have read above means that the PNG format is more susceptible to this than 
any other format (JPG for example) and I think that these days such tricks 
are fairly well locked down by the OS, and by anti virus programs.

Mike

|
| "A PNG file or datastream is composed of a collection of explicitly
| typed "chunks". Chunks whose contents are defined by the specification
| could actually contain anything, including malicious code. But there is
| no known risk that such malicious code could be executed on the
| recipient�s computer as a result of decoding the PNG image. The possible
| security risks associated with future chunk types cannot be specified at
| this time." (section 5, pg 33, pgph 2-3)
|
  It does use "chunks" with alphabetic labels to
order the file content. In that way it's designed for
expandability. New chunk types can be added and
software can be updated to recognize the new types.

  I have VB code for opening/reading PNGs. Only a
few chunk types are required for that. Others can just
be ignored. So sometime down the line someone might
create a chunk type with the name "EVIL" and write
a nasty function in there. But it wouldn't matter because
no graphic software will recognize that chunk. They'll
just ignore it. Even if they did recognize it, they'd need
to do something with the data. It's not as though a
graphic viewer is finding chunks and just executing the
bytes that follow. 

Mike Williams wrote:
> Well I don't think that's a problem specific to PNG files. Malicious
> code can be contained inside almost any data file. Any code, including
> malicious code, is just a bunch of numbers, in the same way that image
> data (for example) is just a bunch of numbers. The hard part (from a
> trojan writer's point of view!) is in getting that code to run. I don't
> actually know anything at all about writing trojans, but I seem to
> recall reading that in certain circumstances it is possible to do get
> contained data to run as code by arranging the data in such a way that a
> legitimate application which is reading the file gets "tricked" by
> certain blocks of data not being quite what it was expecting, causing
> the application to overwrite the area of memory it had been allocated
> for writing into and causing a buffer overflow. I think it is sometimes
> possible to craft the data in such a way that the processor ends up
> executing code at an address supplied by the data on return from the
> error. Something like that, anyway. I don't think what you have read
> above means that the PNG format is more susceptible to this than any
> other format (JPG for example) and I think that these days such tricks
> are fairly well locked down by the OS, and by anti virus programs.
>
> Mike

I have dream, I have a dream of world where this kind of vulnerabilities 
were non-existent. ..Oh boy! I'm delusional now :)

Getting back to Earth... Can you imagine, how can I explain a regular 
folk or computer illiterate that one could get infected by just reading 
a Webpage or diplaying an image? It's like explaining to them that they 
could get harmed and infected by just opening a book or magazine for 
reading.

Mayayana wrote:

>    It [PNG] does use "chunks" with alphabetic labels to
> order the file content. In that way it's designed for
> expandability. New chunk types can be added and
> software can be updated to recognize the new types.

I like expandability :)

>    I have VB code for opening/reading PNGs. Only a
> few chunk types are required for that. Others can just
> be ignored. So sometime down the line someone might
> create a chunk type with the name "EVIL" and write
> a nasty function in there. But it wouldn't matter because
> no graphic software will recognize that chunk. They'll
> just ignore it. Even if they did recognize it, they'd need
> to do something with the data. It's not as though a
> graphic viewer is finding chunks and just executing the
> bytes that follow.

I see. Interesting details Mayayana. Thanks for explaining this!

I wonder whether there has been a case of infections or attacks via 
opening data files in the past.

"Nando" <hightech@att.net.no.to.sp.am> wrote in message 
news:%23MUVeyLPLHA.5100@TK2MSFTNGP02.phx.gbl...

> I wonder whether there has been a case of infections
> or attacks via opening data files in the past.

    http://www.microsoft.com/technet/security/bulletin/ms04-028.mspx

Mike

"Nando" <hightech@att.net.no.to.sp.am> schrieb im Newsbeitrag
news:us3egtLPLHA.5768@TK2MSFTNGP06.phx.gbl...

> Getting back to Earth... Can you imagine, how can
> I explain a regular folk or computer illiterate that one
> could get infected by just reading a Webpage or
> diplaying an image? It's like explaining to them that they
> could get harmed and infected by just opening a book
> or magazine for reading.

Now, when you think about it a little - there's really
not much of a difference.

If you're asking me (constantly) about borrowing
my always latest computer-journal or paperback
(or whatever printed media) ... without returning
the favour that means... then I may decide, to spray
the pages the next time with something that gives you
"horrible runs" the next few days.

So, what it always and everywhere boils down to is, that:
1. You need to trust the source!
2. Your own backups are a good idea.
3. You shouldn't behave stupid ... ;-)

Olaf

"Nando" <hightech@att.net.no.to.sp.am> wrote in message 
news:us3egtLPLHA.5768@TK2MSFTNGP06.phx.gbl...

> Getting back to Earth... Can you imagine, how can I explain
> a regular folk or computer illiterate that one could get infected
> by just reading a Webpage or diplaying an image?

Actually I think those people would be the easiest to explain it to. The 
average Joe Public knows only that computers can get viruses, and that you 
are much more likely to get them if you do not pay annual subscriptions to 
one of the large anti-virus and internet security companies and if you fail 
to upgrade to the next all singing all dancing superbly better and safer 
version of Micro$oft Windoze each time a new version is released. Now I 
wonder who writes most of these new viruses that cause people to keep 
spending their money in such a way? I wonder who might have the most to gain 
financially from it . . . hmmm . . .

Mike

Mike Williams wrote:

> Now I wonder who writes most of these new viruses
> that cause people to keep spending their money in such a way? I wonder
> who might have the most to gain financially from it . . . hmmm . . .

I remember the days when anti-virus software had a virus database of 
6000 (that was when Win31 was around), today they are nearly 3 million!

Mike Williams wrote:
> Nando wrote:
>> I wonder whether there has been a case of infections
>> or attacks via opening data files in the past.
>
> http://www.microsoft.com/technet/security/bulletin/ms04-028.mspx

" Buffer Overrun in JPEG Processing (GDI+) Could Allow Code Execution. 
Maximum Severity Rating: Critical. Recommendation: Customers should 
apply the update immediately. "

" A buffer overrun  vulnerability exists in the processing of JPEG image 
formats that could allow remote code execution on an affected system. "

" An attacker who successfully exploited this vulnerability could take 
complete control of an affected system. "


Aha!!!

So I guess software defect is no longer taken seriously. I remember 
companies like Rational fully dedicated to debug enterprise software. It 
seems MS does not invest in software defect detection, and programmers 
don't read books like Code Complete anymore. No longer important for the 
industry I guess ? Consumers have already learned to just keep upgrading 
and rebooting for patches.

On 17/08/2010 04:19, Nando wrote:
> Mike Williams wrote:
>> Nando wrote:
>>> I wonder whether there has been a case of infections
>>> or attacks via opening data files in the past.
>>
>> http://www.microsoft.com/technet/security/bulletin/ms04-028.mspx
>
> " Buffer Overrun in JPEG Processing (GDI+) Could Allow Code Execution.
> Maximum Severity Rating: Critical. Recommendation: Customers should
> apply the update immediately. "
>
> " A buffer overrun vulnerability exists in the processing of JPEG image
> formats that could allow remote code execution on an affected system. "
>
> " An attacker who successfully exploited this vulnerability could take
> complete control of an affected system. "
>
>
> Aha!!!
>
> So I guess software defect is no longer taken seriously. I remember
> companies like Rational fully dedicated to debug enterprise software. It
> seems MS does not invest in software defect detection, and programmers
> don't read books like Code Complete anymore. No longer important for the
> industry I guess ? Consumers have already learned to just keep upgrading
> and rebooting for patches.

And you can create thousands of lines of code which are 100% bug free?
Bugs exist. You can test for some things, but it is impossible to test 
for every combination.
Once you know about it, it's (normally) easy to fix, but you have to 
have an idea of what to look for...

-- 
Dee Earley (dee.earley@icode.co.uk)
i-Catcher Development Team

iCode Systems

(Replies direct to my email address will be ignored.
Please reply to the group.)

On 15/08/2010 04:33, Nando wrote:
> Thanks a lot Mike! That solves the mystery. Hope there isn't any file
> format out-there implementing my wild thought of embedding decompression
> engines ;)

UPX does, but then it's an executable anyway so expected.

-- 
Dee Earley (dee.earley@icode.co.uk)
i-Catcher Development Team

iCode Systems

(Replies direct to my email address will be ignored.
Please reply to the group.)

http://www.planet-source-code.com/vb/scripts/ShowCode.asp?txtCodeId=72401&lngWId=1


"Nando" <hightech@att.net.no.to.sp.am> wrote in message 
news:uflaC5aMLHA.2100@TK2MSFTNGP06.phx.gbl...
| Hi all! I have a little program (written in VB6) that saves the image in
| a picturebox to a BMP file. The problem is that BMP files are several
| megabytes in size and do not support DPI (dots-per-inch) information for
| printing.
|
| I have turned to the PNG format which provides lossless compression
| (files are only few kilobytes) and includes DPI information.
|
| But how do I save the image in a picturebox to a PNG file?
|
| Thanks in advance! 

Abhishek wrote:
> http://www.planet-source-code.com/vb/scripts/ShowCode.asp?txtCodeId=72401&lngWId=1

Thanks Abhishek!!

> Nando wrote:
> | Hi all! I have a little program (written in VB6) that saves the image in
> | a picturebox to a BMP file. The problem is that BMP files are several
> | megabytes in size and do not support DPI (dots-per-inch) information for
> | printing.
> |
> | I have turned to the PNG format which provides lossless compression
> | (files are only few kilobytes) and includes DPI information.
> |
> | But how do I save the image in a picturebox to a PNG file?
> |
> | Thanks in advance!