Firstly, I'd like to propose a slight change to the scanlines example so
that it is easier for developers to follow the code and to possibly
incorporate bits of it into their own code.
type
TBGRA = packed record
b, g, r, a : byte;
end;
PBGRA = ^TBGRA;
TBGRAArray = array[ WORD ] of TBGRA;
PBGRAArray = ^TBGRAArray;
procedure TForm1.PaintToRGB32bitScanLine(Row, ImgWidth: integer;
LineStart: Pointer);
// LineStart is pointer to the start of a scanline with the following
format:
// 4 bytes per pixel. First byte is blue, second green, third is red.
// the fourth byte is the Alpha value, which is not specified in this
// example
// Black is 0,0,0, white is 255,255,255
var
i: Integer;
lrow : PBGRAArray
begin
lrow := PBGRAArray( LineStart )
// fill line with gray
for i := 0 to ImgWidth - 1 do
begin
lrow^[ i ].r := 128; // set red to 128
lrow^[ i ].g := 128; // set green to 128
lrow^[ i ].b := 128; // set blue to 128
end;
// set one diagonal pixel to red ( this creates a diagonal red line )
lrow^[ ( Row mod ImgWidth ) ].r := 255; // set red to 255 - full
intensity
lrow^[ ( Row mod ImgWidth ) ].g := 0; // set green to 0
lrow^[ ( Row mod ImgWidth ) ].b := 0; // set blue to 0
end;
I think this is a lot easier to understand than the previous version.
Secondly, I have a scanline issue that I hope someone on here can help
with. I have 2 TImages on a Form ( I'm using Mac OS X if that makes any
difference ) one contains an image of a yellow light bulb. I want to
copy, pixel by pixel, the image from one TImage over to the second
TImage. Yes I know I could just assign the bitmap from one to the other,
but this is an exercise in Scanline manipulation. The problem I have is
that once copied the second TImage contains a blue light bulb instead of
a yellow one.
The code I'm using is..
MyBitmap := TBitmap.Create;
ScanLineImage := Image1.Picture.Bitmap.CreateIntfImage;
MyBitmap.Width := ScanLineImage.Width;
MyBitmap.Height:= ScanLineImage.Height;
IntfImage := MyBitmap.CreateIntfImage;
ImgFormatDescription.Init_BPP32_B8G8R8_BIO_TTB( ScanLineImage.Width,
ScanLineImage.Height );
IntfImage.DataDescrption := ImgFormatDescription;
for y := 0 to ScanLineImage.Height do
begin
lrow := ScanLineImage.GetDataLineStart( y );
brow := IntfImage.GetDataLineStart( y );
for x := 0 to ScanLineImage.Width do
begin
brow^[ x ].r := lrow^[ x ].r; // set red
brow^[ x ].g := lrow^[ x ].g; // set green
brow^[ x ].b := lrow^[ x ].b; // set blue
brow^[ x ].a := lrow^[ x ].a; // set alpha value
end;
end;
MyBitmap.LoadFromIntfImage( IntfImage );
Image2.Picture.Bitmap := MyBitmap;
Can anyone see a flaw in my logic of using scanlines for this/this way?
Thanks,
Dominique.
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