How to convert TBitMap 32bit to 24bit? [solved]
lazarus / 39-Graphics

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Demi · 2013-02-20 11:17

Hello everybody!

Code: [Select] bmap:=TBitMap.Create;
 bmap.Assign(Bitmap);  //  Bitmap is 32bit.
 bmap.PixelFormat:=pf24bit;  // Result - black rectangle
How to convert TBitMap 32bit to 24bit?

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circular · 2013-02-20 12:10

Do you mean changing the encoding, or filling the alpha value with
"opaque" ?

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Demi · 2013-02-20 12:34

I want to change the bit depth images. Image of 32-bit can not be
printed on some printers.

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circular · 2013-02-20 12:40

Maybe with two LazIntfImage, one of 32-bit, one of 24-bit. Or by
writing it to a stream and reading it again in a 24-bit bitmap.

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Demi · 2013-02-20 13:20

I can not find how to make a 24-bit LazIntfImage. ((

Code: [Select]
 test:=TLazIntfImage.Create(Bitmap.Width,Bitmap.Height);
 test.LoadFromBitmap(Bitmap.Handle,Bitmap.MaskHandle); 

 bmap.LoadFromIntfImage(test);
 bmap.PixelFormat:=pf24bit;

 if bmap.PixelFormat = pf24bit then
  Form1.Caption:='24';

 if bmap.PixelFormat = pf32bit then
  Form1.Caption:='32';      


Result: Form1.Caption = 32

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circular · 2013-02-20 13:38

I'm not sure you can assign PixelFormat like that. I've read somewhere
that it is only provided for compatiblity with Delphi.

In this example, I suppose you need to change the format of
TLazIntfImage itself.

So first set the DataDescription property of the LazIntfImage, then
put the bitmap inside, and then load the bitmap from the LazIntfImage.

Note that maybe LoadFromBitmap replaces the DataDescription, so you
may need an additionnaly TLazIntfImage to load the bitmap, and to copy
it you can for example use the Colors property.

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Demi · 2013-02-20 14:47

Code: [Select]
test1:=TLazIntfImage.Create(Bitmap.Width,Bitmap.Height);
 test:= Bitmap.CreateIntfImage;
 ImgFormatDescription.Init_BPP24_B8G8R8_BIO_TTB(Bitmap.Width,Bitmap.He
ight);
 test1.DataDescription:=ImgFormatDescription;
 test1.CopyPixels(test);     
 bmap:=TBitMap.Create;
 bmap.PixelFormat:=pf24bit;
 bmap.LoadFromIntfImage(test1); 

 if bmap.PixelFormat = pf24bit then
  Form1.Caption:='24';   //   it's work!!!! Form1.Caption=24

 if bmap.PixelFormat = pf32bit then
  Form1.Caption:='32';
              

This code creates a 24-bit image. But all the transparent pixels
become black. ((
Result: https://dl.dropbox.com/u/19158664/screen.jpg

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circular · 2013-02-20 14:49

You need to copy pixels with a loop, and for each pixel, replace the
alpha value with 65535

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Demi · 2013-02-21 06:34

Thank you! It works!
I make copy images (24-bit) for print. This images load to TImageList.

Get image:

Code: [Select] PrintList.GetBitmap(SelectLIm.tag,b); // b - 32-bit
image (((

Print image:

 Dest.StretchDraw(DestRect,b); // print black rectangle

Code: [Select]Procedure
Draw32Image(Dest:TCanvas;DestRect:TRect;Bitmap: TBitmap);  // Print
32-bit image to Printer.canvas.
var
  bmap:TBitMap;
  test,test1:TLazIntfImage;
  ImgFormatDescription: TRawImageDescription;
begin
 test1:=TLazIntfImage.Create(Bitmap.Width,Bitmap.Height);
 test:= Bitmap.CreateIntfImage;
 ImgFormatDescription.Init_BPP24_B8G8R8_BIO_TTB(Bitmap.Width,Bitmap.He
ight);
 test1.DataDescription:=ImgFormatDescription;
 test1.CopyPixels(test);
 bmap:=TBitMap.Create;
 bmap.PixelFormat:=pf24bit;
 bmap.LoadFromIntfImage(test1);
 Dest.StretchDraw(DestRect,bmap);
 bmap.free;
 test.free;
 test1.Free;
end;

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circular · 2013-02-21 07:11

euh, that's the previous code ?