Как изменить яркость и контраст?
Falk0ner, вс, 06/07/2008 - 15:35.
Взято с Delphi Knowledge Base: http://www.baltsoft.com/
You must change the RBG values of the pixels. For 1, 4 and 8 bit bitmaps, you must edit the palette. For 15 - 32 bit bitmaps, you must edit the pixel direct. For larger bitmaps you should precalulate a table and set the RGB values from this table.
Red := BCTable[Red];
Green := BCTable[Green];
Blue := BCTable[Blue];
You can find the calculation of the table below. The rest is standard source code, look at EFG's Computer Lab for any solution.
I define the brightness and contrast value between 0..255. Other definitions are possible, change BMax, CMax, BNorm and CNorm.
type
TBCTable = array[Byte] of Byte;
const
RGBCount = 256;
RGBMax = 255;
RGBHalf = 128;
RGBMin = 0;
BMax = 128; { Maximal value brightness 100% - 0% = 0% - - 100% }
CMax = 128; { Maximal value contrast 100% - 0% = 0% - - 100% }
BNorm = 128; { Normal value brightness 0% }
CNorm = 128; { Normal value contrast 0% }
procedure CalcBCTable(var ABCTable: TBCTable; ABrightness, AContrast: Integer);
var
i, v: Integer;
BOffset: Integer;
M, D: Integer;
begin
Dec(ABrightness, BNorm);
Dec(AContrast, CNorm);
{ precalculation brightness assistance values }
BOffset := ((ABrightness) * RGBMax div BMax);
{ precalculation contrast assistance values }
if AContrast < CMax then
begin { because Division by 0 on 100% }
if AContrast <= 0 then
begin { decrement contrast }
M := CMax + AContrast;
D := CMax;
end
else
begin { increment contrast }
M := CMax;
D := CMax - AContrast;
end;
end
else
begin
M := 0;
D := 1;
end;
for i := RGBMin to RGBMax do
begin
{ calculate contrast }
if AContrast < CMax then
begin
v := ((i - RGBHalf) * M) div D + RGBHalf;
{ restrict to byte range }
if v < RGBMin then
v := RGBMin
else if v > RGBMax then
v := RGBMax;
end
else
begin { contrast = 100% }
if i < RGBHalf then
v := RGBMin
else
v := RGBMax;
end;
{ calculate brightness }
Inc(v, BOffset);
{ restrict to byte range }
if v < RGBMin then
v := RGBMin
else if v > RGBMax then
v := RGBMax;
ABCTable[i] := v;
end;
end;
TBCTable = array[Byte] of Byte;
const
RGBCount = 256;
RGBMax = 255;
RGBHalf = 128;
RGBMin = 0;
BMax = 128; { Maximal value brightness 100% - 0% = 0% - - 100% }
CMax = 128; { Maximal value contrast 100% - 0% = 0% - - 100% }
BNorm = 128; { Normal value brightness 0% }
CNorm = 128; { Normal value contrast 0% }
procedure CalcBCTable(var ABCTable: TBCTable; ABrightness, AContrast: Integer);
var
i, v: Integer;
BOffset: Integer;
M, D: Integer;
begin
Dec(ABrightness, BNorm);
Dec(AContrast, CNorm);
{ precalculation brightness assistance values }
BOffset := ((ABrightness) * RGBMax div BMax);
{ precalculation contrast assistance values }
if AContrast < CMax then
begin { because Division by 0 on 100% }
if AContrast <= 0 then
begin { decrement contrast }
M := CMax + AContrast;
D := CMax;
end
else
begin { increment contrast }
M := CMax;
D := CMax - AContrast;
end;
end
else
begin
M := 0;
D := 1;
end;
for i := RGBMin to RGBMax do
begin
{ calculate contrast }
if AContrast < CMax then
begin
v := ((i - RGBHalf) * M) div D + RGBHalf;
{ restrict to byte range }
if v < RGBMin then
v := RGBMin
else if v > RGBMax then
v := RGBMax;
end
else
begin { contrast = 100% }
if i < RGBHalf then
v := RGBMin
else
v := RGBMax;
end;
{ calculate brightness }
Inc(v, BOffset);
{ restrict to byte range }
if v < RGBMin then
v := RGBMin
else if v > RGBMax then
v := RGBMax;
ABCTable[i] := v;
end;
end;
Add a fixed value and clip it to the range. I have used a LUT, which is faster for larger bitmaps. The range of Brightness is -255 (-100%) to 255 (+100%). You can use a 32 or 24 Bit calculation depending on the compiler setting ChangeBrightness24Bit.
procedure ChangeBrightness(Bitmap: TBitmap; Brightness: Integer);
var
LUT: array[Byte] of Byte;
v, i: Integer;
{$IFDEF ChangeBrightness24Bit}
w, h, x, y: Integer;
LineSize: LongInt;
pLineStart: PByte;
{$ENDIF}
p: PByte;
begin
{ create LUT }
for i := 0 to 255 do
begin
v := i + Brightness;
if v < 0 then
v := 0
else if v > 255 then
v := 255;
LUT[i] := v;
end;
{$IFDEF ChangeBrightness24Bit}
{ edit bitmap }
w := Bitmap.Width;
h := Bitmap.Height - 1;
Bitmap.PixelFormat := pf24Bit;
pLineStart := PByte(Bitmap.ScanLine[h]);
{ pixel line is aligned to 32 Bit }
LineSize := ((w * 3 + 3) div 4) * 4;
w := w * 3 - 1;
for y := 0 to h do
begin
p := pLineStart;
for x := 0 to w do
begin
p^ := LUT[p^];
Inc(p);
end;
Inc(pLineStart, LineSize);
end;
{$ELSE}
{ edit bitmap }
Bitmap.PixelFormat := pf32Bit;
p := PByte(Bitmap.ScanLine[Bitmap.Height - 1]);
for i := 0 to Bitmap.Width * Bitmap.Height - 1 do
begin
p^ := LUT[p^];
Inc(p);
p^ := LUT[p^];
Inc(p);
p^ := LUT[p^];
Inc(p, 2);
end;
{$ENDIF}
end;
var
LUT: array[Byte] of Byte;
v, i: Integer;
{$IFDEF ChangeBrightness24Bit}
w, h, x, y: Integer;
LineSize: LongInt;
pLineStart: PByte;
{$ENDIF}
p: PByte;
begin
{ create LUT }
for i := 0 to 255 do
begin
v := i + Brightness;
if v < 0 then
v := 0
else if v > 255 then
v := 255;
LUT[i] := v;
end;
{$IFDEF ChangeBrightness24Bit}
{ edit bitmap }
w := Bitmap.Width;
h := Bitmap.Height - 1;
Bitmap.PixelFormat := pf24Bit;
pLineStart := PByte(Bitmap.ScanLine[h]);
{ pixel line is aligned to 32 Bit }
LineSize := ((w * 3 + 3) div 4) * 4;
w := w * 3 - 1;
for y := 0 to h do
begin
p := pLineStart;
for x := 0 to w do
begin
p^ := LUT[p^];
Inc(p);
end;
Inc(pLineStart, LineSize);
end;
{$ELSE}
{ edit bitmap }
Bitmap.PixelFormat := pf32Bit;
p := PByte(Bitmap.ScanLine[Bitmap.Height - 1]);
for i := 0 to Bitmap.Width * Bitmap.Height - 1 do
begin
p^ := LUT[p^];
Inc(p);
p^ := LUT[p^];
Inc(p);
p^ := LUT[p^];
Inc(p, 2);
end;
{$ENDIF}
end;
Взято с Delphi Knowledge Base: http://www.baltsoft.com/
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