Division by zero using TRawImage Init_BPP24_R8G8B8_BIO_TTB on linux 64
lazarus / 39-Graphics

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jcbritobr · 2022-08-03 21:37

Hello, good afternoon. Im reading about TLazIntfImage and Im working
with this object on linux 64. I perceived that using
Init_BPP24_R8G8B8_BIO_TTB in code below leads to division by zero
error. Cant understand why 32 bit images are working, and 24 bit the
issue happens. May someone help?

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 var 
AImage: TLazIntfImage;  lRawImage: TRawImage;begin  lRawImage.Init; 
lRawImage.Description.Init_BPP32_A8R8G8B8_BIO_TTB(100, 100); 
lRawImage.CreateData(False);  AImage := TLazIntfImage.Create(0, 0); 
try    //AImage.DataDescription := GetDescriptionFromDevice(0);   
//AImage.SetSize(0, 0);    AImage.SetRawImage(lRawImage);    try     
ImgMain.Picture.Bitmap.LoadFromIntfImage(AImage); // ---division by
zero here when using 24bpp image---    except      on E: Exception do 
      ShowMessage('An exception was raised: ' + E.Message);    end; 
finally    AImage.Free;  end;

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dje · 2022-08-17 14:04

You may need to do some tracing at your end.

TBitmap is derived from TRasterImage.
TRasterImage.LoadFromIntfImage(IntfImage: TLazIntfImage) calls
IntfImage.CreateBitmaps()
IntfImage.CreateBitmaps calls RawImage_CreateBitmaps for the platform
widget set.

I'm using Gtk, so when I searched the LCL source for
RawImage_CreateBitmaps, I can find the implementations for GTk.
I can see a number of comments like:
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 // check if
the depth is supported  // try some alternative (I'm not sure if we
should fail here instead)// if we don't have a visual we cannot draw
anyway      // this is only a rough implementation, there is no check
against bitsperpixel   // The gdk_pixmap_create_from_data creates only
a two-color pixmap so we can not use it// this is only a rough
implementation, there is no check against bitsperpixel
The point being, my system throws a 'Failed to create handles'. Which
means, the pixel format was identified as "not supported", and failed
correctly. I checked a couple of the 24bit pixel formats, and they all
failed. This is the ideal result.

I didn't get a divide by zero, so I'm guessing, whatever setup you
have, is passing though a safety check and hitting a div/divmod
command.

Either way, it looks like 24bit rawimages have little to no bitmap
handle support. (Most likely because its not possible)

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jcbritobr · 2022-08-22 19:55

Hello. Thank you. I really apreciate your answer.
In my environment, that is linux 64, and also using gtk I got division
by zero from a unit. I had read the comments but none about no support
for 24pp. I think its a bad error handling. Maybe an exception with
"Not supported" text gets better.