Delphi - PNG Images

For web pages, images are typically in either jpeg or png format. The image editor supplied with Delphi 5 does not supply either of those. Windows Paint

Start / Programs / Accessories / Paint
%SystemRoot%\system32\mspaint.exe

provides both. I eventually got tired of using Windows Paint to document my programs .. so I wrote my own screen capture utility.

Delphi 5 provides a unit to create jpeg files, but not png. (More recent versions contain png support.)

This page discusses using

PNG Delphi v.1.564   282 k   02 Feb 2008
By Gustavo Daud

in Delphi 5 to provide png support.

Overview | Save PNG File | A Test Case

Overview

Several forums suggest using TPNGImage by Gustavo Daud but claim that it is no longer available on sourceforge. It turns out that as of June 2014, they are correct. Luckily, I found part of it available on Torry's Delphi page.

torry.net - indicates that the code is FWS - Free with source code
sourceforge - a page, but no files

The comments indicate that it works with D2005 D2006 D2007 D6 D7, but not Delphi 5 (D5) .. so I took a chance. The zip contains source code, a few object files, and a help file.

The help file says that there is one package file per Delphi version .. and to use the correct one. Well, there aren't any package files! So I created one.

Create a new package
Be sure to name the package (save it) before compiling it!!!
Add all 4 source files in pngimage.zip
Press Compile
There will be several warnings - I just ignored them
Press Install

That's all there is to it. There will be a new "button" added to the Samples tab - but it just has a default icon since there was no resource file in the zip. (The code example in the next section does not use this.)

Save PNG File

This is the code I used - no big deal.

uses pngimage;

  procedure Save_bitmap_as_png_file_mc(bitmap: TBitmap; FileName: string);

procedure Save_bitmap_as_png_file_mc(bitmap: TBitmap; FileName: string);
var
  png: TPNGObject;  //Requires the "pngImage" unit added to "uses" clause.
  ext : string;
begin
  ext := ExtractFileExt(FileName) ;
  if SameText(ext, '.png') then begin

     // based on code from help - pngimage\PngDelphi.chm
    png := TPNGObject.Create;
    try
      png.Assign(Bitmap);
      png.SaveToFile(FileName);
    finally
      png.Free;
    end;
  end;
end;

It works using Delphi 5 on Windows XP.

A Test Case

Using a single image, these are the file sizes

jpeg	Delphi TJpegImage at max quality	138 kb
png	Delphi TPNGObject	18 kb
png	MS Paint	23 kb

I was not able to detect any visual difference between the files.

Author: Robert Clemenzi