[Solved] PNGImageException 'Chunk length exceeds stream length'
lazarus / 39-Graphics

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lainz · 2019-12-30 20:30

I'm getting the error PNGImageException 'Chunk length exceeds stream
length'


I'm using the unit posted here:
https://forum.lazarus.freepascal.org/index.php/topic,47901.msg344243.h
tml#msg344243

With this code I can not replicate the error, but is the same I'm
doing in my application that's really big and propietary so I can not
post it, but this is the intended use:
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i procedure
TForm1.Button1Click(Sender: TObject);var  LBuffer : rawbytestring; 
stream: TFileStream;  s: TStringList;begin  LBuffer := #27'@'; //
Initialise the printer  s := TStringList.Create; 
s.LoadFromFile(Application.Location + 'logo.txt');  LBuffer := LBuffer
+ _ESCPosPrintBitmap().RenderBitmapBase64(s.Text);  s.Free;   stream
:= TFileStream.Create('logo.bin', fmCreate);  try   
stream.Write(LBuffer[1], Length(LBuffer));  finally    stream.Free; 
end;end;
Whit this base64 image:
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i data:image/
png;base64,iVBORw0KGgoAAAANSUhEUgAAAQQAAAEECAYAAADOCEoKAAAR/klEQVR4Xu2
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=
The application is in mode objfpc, the ssESCPosPrintBitmap.pas from
the other post is in mode delphi.

What can be causing the issue, I tested the image and it's a valid PNG
image... any ideas?

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circular · 2019-12-30 20:45

I suspect a bit of the stream is not saved for some reason.

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lainz · 2019-12-30 20:54

What puzzles me is that in the demo project everything works fine, but
when I want to incorporate to the application the error occurs.

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Cyrax · 2019-12-30 21:26

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i type 
IssESCPosPrintBitmap = interface( IInterface )     
['{3F279585-6D2E-451F-AF97-76F0E07A70DF}']      function RenderBitmap(
const ABitmapFilename: string ): rawbytestring;      function
RenderBitmapBase64(const base64data: string): rawbytestring;  end; 
What about changing all occurrences of string type to rawbytestring
one? Does that help?

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lainz · 2019-12-30 21:37

Hi, it does nothing. :S

Also the function DecodeStringBase64(const
s:string;strict:boolean=false):String; expects and returns strings.

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winni · 2019-12-30 21:51

Hi!

Try to save the file without a stream but the old fashioned way:

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i varf : file
of byte;  
 .....assignFile(F,application.location+'logo.bin');rewrite(f);for i
:= 1 to length(LBuffer) do write(f,ord(LBuffer[i]));closeFile(f);    
                                       

Look if now still an error occurs.

Winni

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lainz · 2019-12-30 21:55

Thanks. I found the problem and it was outside the scope of the demo
project, sorry 

The problem was that the TBufDataset for some reason loaded only a
part of the base64 string.

Changed that line and it works.