Mega Code Archive
Transform a TImage.Picture.Bitmap to GrayScale
<![CDATA[
Title: Transform a TImage.Picture.Bitmap to GrayScale
Question: A TBitmap object has no method to convert to GrayScale mode.
Answer:
However, you can transform a Bitmap to GrayScale with the following procedure:
procedure ImageGrayScale(var AnImage: TImage);
var
JPGImage: TJPEGImage;
BMPImage: TBitmap;
MemStream: TMemoryStream;
begin
BMPImage := TBitmap.Create;
try
BMPImage.Width := AnImage.Picture.Bitmap.Width;
BMPImage.Height := AnImage.Picture.Bitmap.Height;
JPGImage := TJPEGImage.Create;
try
JPGImage.Assign(AnImage.Picture.Bitmap);
JPGImage.CompressionQuality := 100;
JPGImage.Compress;
JPGImage.Grayscale := True;
BMPImage.Canvas.Draw(0, 0, JPGImage);
MemStream := TMemoryStream.Create;
try
BMPImage.SaveToStream(MemStream);
//you need to reset the position of the MemoryStream to 0
MemStream.Position := 0;
AnImage.Picture.Bitmap.LoadFromStream(MemStream);
AnImage.Refresh;
finally
MemStream.Free;
end;
finally
JPGImage.Free;
end;
finally
BMPImage.Free;
end;
end;//fin de ImageGrayScale
//MWMWMWMWMWMWMWMWMWMWMWMWMWMWMWMWMWMWMWMWMWMWMWMWMWMWMWMWMWMWMWMWMWM
The trick is to assign the content of the Bitmap to a JPEGImage, which has a GrayScale property, and then copy the content of the JPEGImage back to Bitmap, using a MemoryStream.
The only drawback is using a JPEGImage, because the JPEGImage has a lousy compression of the image, in other words you loose information with the compression, but the human eye doesnt notice. If you kwnow another implementation please send me an e-mail.
]]>