Raw Image Structure (BGRA) to TBitmap - Fastest way
lazarus / 39-Graphics

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gabriemarcelo · 2019-09-04 13:05

Hi guys... Lets say that I have a raw image structure in memory where
each pixel is stored in BGRA (4 bytes per pixel). I can get the
pointer to that buffer. I need to print or draw it on a Canvas. To
draw that raw image, I create a TBitmap with the same Width & Height
and then loop through each raw pixel BGRA values and set it to the
TBitmap. A snipped code is below... My question is... can I avoid
looping through the raw structure and instead just set the new
TBitmap.RawImage.Data to that pointer? I'd like to avoid creating two
buffers in order to I need to speed up this code... any hints on this?
thanks in advance

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i  // bmpPage
is the BGRA structure in memory... bmp := TBitmap.Create;bmp.Width :=
bmpPage.Width;bmp.Height :=
bmpPage.Height; bmp.BeginUpdate(); bytesPerPixel :=
bmp.RawImage.Description.BitsPerPixel div 8;redOffset :=
bmp.RawImage.Description.RedShift div 8;greenOffset :=
bmp.RawImage.Description.GreenShift div 8;blueOffset :=
bmp.RawImage.Description.BlueShift div 8; ptr :=
bmpPage.GetBuffer; for Y := 0 to bmp.Height - 1 dobegin       
LinePixs := bmp.RawImage.GetLineStart(Y);        for X := 0 to
bmp.Width - 1 do        begin                b := PByte(ptr)^;       
       inc(ptr);                g := PByte(ptr)^;               
inc(ptr);                r := PByte(ptr)^;                inc(ptr);  
            a := PByte(ptr)^;                inc(ptr);               
(LinePixs+blueOffset)^ := b;                (LinePixs+greenOffset)^ :=
g;                (LinePixs+redOffset)^ := r;               
inc(LinePixs, bytesPerPixel);        end;end; bmp.EndUpdate();

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BeanzMaster · 2019-09-05 16:10

Hi, this is the method i'm using in my library

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i function
TBZCustomBitmap.ExportToBitmap : Graphics.TBitmap;var  Temp:    
Graphics.TBitmap;  RawImage: TRawImage;  BitmapHandle, MaskHandle:
HBitmap;  W,H : Integer;  Buffer : PByte;Begin  result := nil; 
BitmapHandle := 0;  MaskHandle := 0;  w := Self.Width;  h:=
 Self.Height;  Buffer := PByte(GetSurfaceBuffer);   RawImage.Init; 
RawImage.Description.Init_BPP32_R8G8B8A8_BIO_TTB(W,H);  RawImage.Data
:= Buffer;  RawImage.DataSize:= Self.Size;   if not
RawImage_CreateBitmaps(RawImage, BitmapHandle, MaskHandle, False)
then  begin    raise EBZBitmapException.Create('Failed to create
bitmap handle');  end  else  begin   Temp := Graphics.TBitmap.Create; 
 Temp.Handle := BitmapHandle;   Temp.MaskHandle := MaskHandle; 
 Result := Temp;  end;  if (Result=nil) then Raise
EBZBitmapException.Create('Erreur de conversion vers TBitmap');End;
"GetSurfaceBuffer" return my raw buffer in (bgra or rgba format depend
the os)

Cheers

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gabriemarcelo · 2019-09-05 21:47

thanks for sharing the code. I tested it but it does not work as
expected because my raw image format is BGRA and your code assumes
it's RGBA as in your code you call Init_BPP32_R8G8B8A8_BIO_TTB
The code runs but the output image has wrong pixel values as expected
because again, my source is BGRA.

If I change that call to this one (which should be the correct for
BGRA format)  Init_BPP32_B8G8R8A8_M1_BIO_TTB then the code fails at
that procedure (error Image attached).

Do you know why?

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BeanzMaster · 2019-09-06 18:13

Hi,

in your code Size is incorrect. It's (w*h) *4 (4 is for BGRA or RGBA.
One byte per channel  ) so try an tell us
And also becarefull with your "Buffer" it must be a PByte. I don't
known what is your structure exactly.

Cheers

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gabriemarcelo · 2019-09-06 19:28

That did the trick! Thanks a lot. Regards,

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gabriemarcelo · 2019-09-06 21:36

Bad news... the code fails in macOS compiling to Cocoa 64bit apps...
the code fails in the RawImage_CreateBitmaps (in the cocoalclintf.inc)
more precisely in the RawImage_DescriptionToBitmapType which is not
implemented for BGRA as it's not listed in the TCocoaBitmapType  ...
Did you test your code in macOS cocoa?

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BeanzMaster · 2019-09-09 19:13

Hi, sorry ,i can't test actually with Mac and don't know how Cocoa64
scheme. But perhaps the trick will be to create an RGBA raw image, and
so you'll must swap R&B of your buffer before export it.

This how i swap R&B

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i // Fast
Red-Blue channel color swappingType   TBZColor =record // Very
simplified record of my solution  Case Integer of     //0 : (Red,
Green, Blue, Alpha : Byte); For Linux, Mac and other     0 : (Blue,
Green, Red, Alpha : Byte); //For Windows     1 : (AsInteger :
Cardina)l;  end;   PBZColor = ^TBZColor;   procedure SwapRB(Buf:
PBZColor; pixelCount: Integer);  var    Pixptr: PBZColor;    AIntColor
: Cardinal;  begin    PixPtr := Buf;    while pixelCount > 0 do   
begin      AIntColor := PixPtr^.AsInteger;      PixPtr^.AsInteger :=
AIntColor and $FF00FF00 or (AintColor and $000000FF SHL 16) or
(AIntColor and $00FF0000 SHR 16);      Inc(PixPtr);     
Dec(pixelCount);    end;  end;