[fpc-devel] Extract the color data and alpha from a PNG image

[Mattias Gaertner]

On Tue, 5 Feb 2013 12:37:24 -0200
silvioprog <silvioprog at gmail.com> wrote:

> Hello friends,
> 
> I'm trying to extract the color data and alpha from a PNG image. In PHP it
> is very easy to implement, but in FPC I don't know how to do it. I tried to
> do it via "chunk.data", "ZData" etc., but, without success.
> 
> Attached two files to test it. To test the PHP code run this command in
> your terminal:
> 
> php -f fpdf.php
> 
> The in FPC code is partially complete.

Have you tried fpimage?

uses
  fpreadpng, fpimage;
 
var
  image: TFPCustomImage;
  reader: TFPCustomImageReader;
  x,y: integer;
  c: TFPColor;
begin
  Image := TFPMemoryImage.Create(0, 0);
  Reader := TFPReaderPNG.Create;
  Image.LoadFromFile(AFileName, Reader);
  for y:=0 to Image.Height-1 do
    for x:=0 to Image.Width-1 do begin
      c:=Image.Colors[x,y];
      writeln(c.Alpha,' ',c.Blue);
    end;
  //...

Mattias