Changing the brightness, contrast, and saturation of an image (Bitmap) in Delphi

Recently, I am working on video processing. I encountered some image processing problems and found the solution code elsewhere.

The code processing result of contrast adjustment looks uncomfortable. I have no time to study it carefully for the moment. I will put it here first.

// Brightness change function changebrightness (BMP: tbitmap; s: integer): Boolean; var P: pbytearray; X, Y: integer; begin try // 24-bit real-color BMP. pixelformat: = pf24bit; BMP. canvas. lock; for Y: = 0 to BMP. height-1 do begin P: = BMP. scanline [y]; for X: = 0 to BMP. width-1 do begin // adjust the R, G, and B components of each pixel point begin if S> 0 then begin P [x * 3]: = min (255, P [x * 3] + S); // It cannot be out of bounds. The value range is 0 ~ 255 p [x * 3 + 1]: = min (255, P [x * 3 + 1] + S); P [x * 3 + 2]: = min (255, P [x * 3 + 2] + S); End else begin P [x * 3]: = max (0, P [x * 3] + S); // It cannot be out of bounds. The value range is-255 ~ 0 p [x * 3 + 1]: = max (0, P [x * 3 + 1] + S); P [x * 3 + 2]: = max (0, P [x * 3 + 2] + S); end; BMP. canvas. unlock; Result: = true; failed t result: = false; end;

// Contrast function changecontrast (BMP: tbitmap; s: integer): Boolean; const cmid = 128; Cmin = 10; Cmax = 246; var P: pbytearray; X, Y: integer; begin try // 24-bit real-color BMP. pixelformat: = pf24bit; BMP. canvas. lock; for Y: = 0 to BMP. height-1 do begin P: = BMP. scanline [y]; for X: = 0 to BMP. width-1 do begin // determine the threshold value as 128 If (P [x * 3]> cmid) and (P [x * 3] <= Cmax) and (P [x * 3 + 1]> cmid) and (P [x * 3 + 1] <= Cmax) and (P [x * 3 + 2]> cmid) and (P [x * 3 + 2] <= Cmax) then begin P [x * 3]: = min (255, P [x * 3] + S * P [x * 3] Div (P [x * 3] + P [x * 3 + 1] + P [x * 3 + 2 ]); P [x * 3 + 1]: = min (255, P [x * 3 + 1] + S * P [x * 3 + 1] Div (P [x * 3] + P [x * 3 + 1] + P [x * 3 + 2]); P [x * 3 + 2]: = min (255, P [x * 3 + 2] + S * P [x * 3 + 2] Div (P [x * 3] + P [x * 3 + 1] + P [x * 3 + 2]); end; If (P [x * 3]> Cmin) and (P [x * 3] <= cmid) and (P [x * 3 + 1]> Cmin) and (P [x * 3 + 1] <= cmid) and (P [x * 3 + 2]> Cmin) and (P [x * 3 + 2] <= cmid) then begin P [x * 3]: = max (0, P [x * 3]-S * P [x * 3] Div (P [x * 3] + P [x * 3 + 1] + P [x * 3 + 2 ]); P [x * 3 + 1]: = max (0, P [x * 3 + 1]-S * P [x * 3 + 1] Div (P [x * 3] + P [x * 3 + 1] + P [x * 3 + 2]); P [x * 3 + 2]: = max (0, P [x * 3 + 2]-S * P [x * 3 + 2] Div (P [x * 3] + P [x * 3 + 1] + P [x * 3 + 2]); end; end; BMP. canvas. unlock; Result: = true; failed t result: = false; end;

// Change the saturation function changesaturation (BMP: tbitmap; valuechange: integer): Boolean; const Cmax = 255; var grays: array [0 .. 767] of integer; Alpha: array [0 .. 255] of word; gray, X, Y: integer; srcrgb: prgbtriple; I: byte; begin valuechange: = valuechange + 255; for I: = 0 to Cmax do begin Alpha [I]: = (I * valuechange) SHR 8; end; X: = 0; for I: = 0 to Cmax do begin Gray: = I-Alpha [I]; grays [x]: = gray; Inc (x); grays [x]: = gray; Inc (x); grays [x]: = gray; Inc (x); end; for Y: = 0 to BMP. height-1 do begin srcrgb: = BMP. scanline [y]; for X: = 0 to BMP. width-1 do begin Gray: = grays [srcrgb. rgbtred + srcrgb. rgbtblue + srcrgb. rgbtgreen]; if Gray + Alpha [srcrgb. rgbtred]> 0 then srcrgb. rgbtred: = min (cmax, gray + Alpha [srcrgb. rgbtred]) else srcrgb. rgbtred: = 0; if Gray + Alpha [srcrgb. rgbtgreen]> 0 then srcrgb. rgbtgreen: = min (cmax, gray + Alpha [srcrgb. rgbtgreen]) else srcrgb. rgbtgreen: = 0; if Gray + Alpha [srcrgb. rgbtblue]> 0 then srcrgb. rgbtblue: = min (cmax, gray + Alpha [srcrgb. rgbtblue]) else srcrgb. rgbtblue: = 0; Inc (srcrgb); end;