Convert PNG to Bitmap

 Download : PNGImage.pas

uses PngImage
//

procedure LoadPngToBmp(var Dest: TBitmap; AFilename: TFilename);
type
  TRGB32 = packed record
    B, G, R, A : Byte;
  end;
  PRGBArray32 = ^TRGBArray32;
  TRGBArray32 = array[0..0] of TRGB32;
type
  TRG24 = packed record
    rgbtBlue, rgbtGreen, rgbtRed : Byte;
  end;
  PRGBArray24 = ^TPRGBArray24;
  TPRGBArray24 = array[0..0] of TRG24;
type
  TByteArray = Array[Word] of Byte;
  PByteArray = ^TByteArray;
  TPByteArray = array[0..0] of TByteArray;
var
  BMP : TBitmap;
  PNG: TPNGObject;
  x, y: Integer; 
  BmpRow: PRGBArray32;
  PngRow : PRGBArray24;
  AlphaRow: PByteArray;
begin
  Bmp := TBitmap.Create;
  PNG := TPNGObject.Create;
  try
    if AFilename <> '' then
    begin
      PNG.LoadFromFile(AFilename);
      BMP.PixelFormat := pf32bit;
      BMP.Height := PNG.Height;
      BMP.Width := PNG.Width;
      if ( PNG.TransparencyMode = ptmPartial ) then
      begin
        for Y := 0 to BMP.Height-1 do
        begin
          BmpRow := PRGBArray32(BMP.ScanLine[Y]);
          PngRow := PRGBArray24(PNG.ScanLine[Y]);
          AlphaRow := PByteArray(PNG.AlphaScanline[Y]);
          for X := 0 to BMP.Width - 1 do
          begin
            with BmpRow[X] do
            begin
              with PngRow[X] do
              begin
                R := rgbtRed; G := rgbtGreen; B := rgbtBlue;
              end;
              A := Byte(AlphaRow[X]);
            end;
          end;
        end;
      end else
      begin
        for Y := 0 to BMP.Height-1 do
        begin
          BmpRow := PRGBArray32(BMP.ScanLine[Y]);
          PngRow := PRGBArray24(PNG.ScanLine[Y]);
          for X := 0 to BMP.Width - 1 do
          begin
            with BmpRow[X] do
            begin
              with PngRow[X] do
              begin
                R := rgbtRed; G := rgbtGreen; B := rgbtBlue;
              end;
              A := 255;
            end;
          end;
        end;
      end;
      Dest.Assign(BMP);
    end;
  finally
    Bmp.Free;
    PNG.Free;
  end;
end;

Beispiel :

procedure TForm1.Button1Click(Sender: TObject);
var bmp : TBitmap;
begin
  bmp := TBitmap.Create;
  if OpenDialog1.Execute then begin
    try
    LoadPngToBmp(bmp, OpenDialog1.FileName);
    bmp.PixelFormat := pf24bit;
    bmp.Transparent := true;
    bmp.SaveToFile(OpenDialog1.FileName + '.bmp');
    finally
    bmp.Free;
    end;
  end;
end;