Bitmap raw data access in Mac OS X / Cocoa
lazarus / 39-Graphics

----------------------------------------------------------------------
agorka · 2018-06-26 12:42

Hello!

I have an lazarus app that runs fine on OS X + Carbon, but since
carbon is going to be deprecated in the next OS X release, I 'm trying
to switch to Cocoa Widgetset.

I'm stuck with direct pixels access. The code that worked in Carbon
doesn't work anymore, RawImage.Data is just returning all zeroes.
I made a small testing procedure:

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 procedure
TForm1.TestBitmaps;var Bmp : TBitmap;beginBmp:=TBitmap.Create;Bmp.Widt
h:=32;Bmp.Height:=32;Bmp.PixelFormat:=pf32bit;Bmp.Canvas.Pixels[0,0]:=
$123456;ShowMessage(ColorToString(Bmp.Canvas.Pixels[0,0]));Bmp.BeginUp
date();Bmp.EndUpdate();ShowMessage(ColorToString(Bmp.Canvas.Pixels[0,0
]));Bmp.Free;end;    First message shows $00123456, but after calling
BeginUpdate / EndUpdate, second message shows $00000000,
so Begin/EndUpdate seem to vipe all the bitmap data.
I tried using LazIntfImage to access pixels, but once again I'm
getting zeroes instead of real color values.

Can anyone help me with that?
I'm using Lazarus 1.8.4/FPC3.0.4
Thanks in advance!

----------------------------------------------------------------------
BeanzMaster · 2018-06-26 13:10

Hi,
Graphics with FCL/LCL are heavy buggy in all OS, like i said in the
topic on my TGIFViewer component. It need to be rework. In waiting i
suggest you try to BGRABitmap instead is very very more stable, and
pretty is pretty cool.  I you can post this issue in the bugtracker

----------------------------------------------------------------------
wp · 2018-06-26 13:27

I tested on Windows and see the same - clBlack after the
Bitmap.EndUpdate.

What do you want to achieve with BeginUpdate/EndUpdate? Investigating
the sources I found that they are used when a TRawImage (an ancestor
of TBitmap) is loaded from a stream or another image. Is it that what
you want to do?

Looking at the declaration of BeginUpdate I see an optional boolean
parameter ACanvasOnly which defaults to False. After setting this to
true (Bitmap.BeginUpdate(true)) the set color is indicated also by the
second ShowMessage.

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 type 
TRasterImage = class(TGraphic)  // TRasterImage is ancestor of
TBitmap  ...    procedure BeginUpdate(ACanvasOnly: Boolean = False); 
 procedure EndUpdate(AStreamIsValid: Boolean = False);  ...end;

----------------------------------------------------------------------
agorka · 2018-06-26 13:42

Thanks for answering!

I made more complex test function:

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 procedure
TForm1.TestBitmaps;var Bmp : TBitmap;    LazIntfImage : TLazIntfImage;
beginBmp:=TBitmap.Create;Bmp.Width:=32;Bmp.Height:=32;Bmp.PixelFormat:
=pf32bit;Bmp.Canvas.Brush.Color:=$234567;Bmp.Canvas.FillRect(0,0,32,32
);LazIntfImage:=Bmp.CreateIntfImage;ShowMessage(ColorToString(Bmp.Canv
as.Pixels[0,0])+'-
LazIntf.Colors:'+IntToStr(LazIntfImage.Colors[0,0].green)+          '-
LazIntf.PixelData:'+IntToStr(LazIntfImage.PixelData[1]));Bmp.BeginUpda
te(True);ShowMessage(ColorToString(Bmp.Canvas.Pixels[0,0])+'-
Raw:'+IntToStr(Bmp.RawImage.Data[1]));Bmp.EndUpdate(False);ShowMessage
(ColorToString(Bmp.Canvas.Pixels[0,0]));Bmp.Free;end;   
On Cocoa I get:
$00234567-LazIntf.Colors:0-LazIntf.PixelData:0
$00234567-Raw:0
$00234567

On Carbon the same code gives:
$00234567-LazIntf.Colors:17733-LazIntf.PixelData:103
$00234567-Raw:103
$00234567

So probably this problem is not caused by BeginUpdate wiping data but
by some raw pixel data copying to RawImage.Data.

Oleg.