I'd love to be able to make all my screenshots in PNG format (which would mean writing to PNG) I've gone as far as to
Here is my incomplete implimentation of a PNG screenshot generator: (taken from Garland's Quest)
Code:
type
TPNGStart = packed Array[0 .. 8] of Byte;
TPNG_IHDR = packed record
Width : DWord;
Height : DWord;
BitDepth : Byte;
ColorType : Byte;
CompressionMethod : Byte;
FilterMethod : Byte;
InterlaceMethod : Byte;
end;
TPNG_Chunk = packed record
Length : DWord;
ChunkType : Array[0 .. 3] of Byte;
ChunkCRC : DWord;
end;
procedure ScreenShot_PNG(Filename: String);
var
i: Integer;
pngStartBytes: TPNGStart;
pngIHDR: TPNG_IHDR;
pngChunk: TPNG_Chunk;
vport: array[0 .. 3] of Integer;
Buffer: PChar;
BufferLength: Integer;
f: TMemoryStream;
crc: Cardinal;
begin
// First 8 bytes //
pngStartBytes[0] := 137;
pngStartBytes[1] := 80;
pngStartBytes[2] := 78;
pngStartBytes[3] := 71;
pngStartBytes[4] := 13;
pngStartBytes[5] := 10;
pngStartBytes[6] := 26;
pngStartBytes[7] := 10;
// Get OpenGL ViewPort Data
glGetIntegerv(GL_VIEWPORT, @vport);
glPixelStorei(GL_PACK_ALIGNMENT, 1);
// Chunk Information //
FillChar(pngChunk, SizeOf(pngChunk), 0);
pngChunk.Length := SizeOf(pngIHDR);
pngChunk.ChunkType[0] := ord('I');
pngChunk.ChunkType[1] := ord('H');
pngChunk.ChunkType[2] := ord('D');
pngChunk.ChunkType[3] := ord('R');
// IHDR Chunk Data //
FillChar(pngIHDR, SizeOf(pngIHDR), 0);
pngIHDR.Width := vport[2];
pngIHDR.Height := vport[3];
pngIHDR.BitDepth := 8;
pngIHDR.ColorType := 2; // 2 = Each pixel is an R,G,B triple. 6 = Each pixel is an R,G,B triple, followed by an alpha sample.
pngIHDR.CompressionMethod := 0; // deflate/inflate compression with a sliding window of at most 32768 bytes
pngIHDR.FilterMethod := 0; // adaptive filtering with five basic filter types
pngIHDR.InterlaceMethod := 0; // 0 (no interlace) or 1 (Adam7 interlace)
// Temp Store Chunk Type & Data into Buffer for processing
BufferLength := (4 + SizeOf(pngIHDR)); // ChunkType + ChunkData
GetMem(Buffer, BufferLength);
for i := 0 to 3 do // Chunk Type to Buffer
Write(Buffer^, pngChunk.ChunkType[i]);
// Write(Buffer^, pngIHDR); // Chunk Data to Buffer
// CRC for Chunk Data //
crc := crc32(0, nil, 0);
// pngChunk.ChunkCRC := crc32(crc, Buffer, BufferLength);
// Start Writing PNG File
f := TMemoryStream.Create;
for i := 0 to 7 do
f.Write(pngStartBytes[0], 1); // First 8 bytes
f.Write(pngChunk.Length, SizeOf(pngChunk.Length)); // IHDR Chunk Length
f.Write(buffer, BufferLength); // IHDR Chunk Type & Data
f.Write(pngChunk.ChunkCRC, SizeOf(pngChunk.ChunkCRC)); // IHDR Chunk CRC
FreeMem(Buffer);
// --- IDAT Chunk --- //
// Chunk Information //
FillChar(pngChunk, SizeOf(pngChunk), 0);
pngChunk.Length := SizeOf(pngIHDR);
pngChunk.ChunkType[0] := ord('I');
pngChunk.ChunkType[1] := ord('H');
pngChunk.ChunkType[2] := ord('D');
pngChunk.ChunkType[3] := ord('R');
// Temp Store Chunk Type & Data into Buffer for processing
BufferLength := (4 + (pngIHDR.Width * pngIHDR.Height * 3)); // rgb
GetMem(Buffer, BufferLength);
glReadPixels(0, 0, vport[2], vport[3], GL_RGB8, GL_UNSIGNED_BYTE, Buffer);
FreeMem(Buffer);
// crc32(crc : cardinal; buf : Pbyte; len : cardinal)
// f.Write(Buffer^, BufferLength);
// IEND Chunk
f.SaveToFile(Filename);
f.Free;
end;
it should work if you can modify it to generate the proper LZH compression for whatever pixel format you will be using. Oh and it is OpenGL dependent.
Originally Posted by User137
What do you mean by this? Lazarus's PNG works without getting anything extra. And after i just opened PNG source files (packages\fcl_image\src) they really don't have anything 3rd party in them.. The one that is included in FPC/Lazarus requires 3rd party libs
. But, it doesn't always load a PNG properly
http://www.eonclash.com/
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