TBitmap color "Search and Replace"
lazarus / 39-Graphics

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ArminLinder · 2017-02-14 20:33

Hi all,

is there a fast way to replace a color with a different color in a
TBitmap, keeping the alpha value unchanged?

What I have is a bunch ob BitBtn buttons on form, each having the
usual  bitmaps for the different button states. Works well. Currently
I have drawn glyphs in shades of black and grey, which fits Windows 7.
On Windows 10 it looks alien, because Windows 10 uses blue color
tones.

The idea is to replace the black shades with blue shades in
FormCreate, so I do not have to maintain two different sets of
bitmaps.

I found some code samples which look promising, but haven't got the
time to do a lengthy trial session tonight, need a quick solution, so
a working code snipped for this would be great.

Thnx

Armin.

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derek.john.evans · 2017-02-14 21:51

Unsure of your exact needs but, its easy to iterate the pixels of a
bitmap via rawimage.

Here is some code to offset the hue:
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 uses
GraphUtil, Math;procedure BitmapOffsetHue(A: TBitmap; AOffset:
integer);var  LHue, LLit, LSat: byte;  LPix, LEnd: PByte;begin 
Assert(A.PixelFormat = pf32bit);  A.BeginUpdate;  try    LPix :=
A.RawImage.Data;    LEnd := LPix + A.RawImage.DataSize - 4;    while
LPix <= LEnd do begin      RGBtoHLS(LPix[2], LPix[1], LPix[0], LHue,
LLit, LSat);      LHue := EnsureRange(LHue + AOffset, 0, 255);     
HLStoRGB(LHue, LLit, LSat, LPix[2], LPix[1], LPix[0]);      Inc(LPix,
4);    end;  finally    A.EndUpdate;  end;end; 
If you have grayscale images you can assign a hue and lightness to
colorize.
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
BitmapColourize(A: TBitmap);var  LHue, LLit, LSat: byte;  LPix, LEnd:
PByte;begin  Assert(A.PixelFormat = pf32bit);  A.BeginUpdate;  try   
LPix := A.RawImage.Data;    LEnd := LPix + A.RawImage.DataSize - 4;  
while LPix <= LEnd do begin      RGBtoHLS(LPix[2], LPix[1], LPix[0],
LHue, LLit, LSat);      LHue := 140;      LSat := 128;     
HLStoRGB(LHue, LLit, LSat, LPix[2], LPix[1], LPix[0]);      Inc(LPix,
4);    end;  finally    A.EndUpdate;  end;end; 
Sometimes I like to load up a paint package to test out what color
effect im looking for, and then try to code up a duplicate effect.

Edit: Small bug fix. You should subtract the pixel size from LEnd just
in case.

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ArminLinder · 2017-02-15 06:39

Hi ...

looks promising. thank you!

Armin.