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Allow selection of ink density

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git-svn-id: file:///srv/svn/repos/haiku/trunk/current@6583 a95241bf-73f2-0310-859d-f6bbb57e9c96
This commit is contained in:
Michael Pfeiffer 2004-02-14 00:00:18 +00:00
parent e2d8351ac4
commit 329e4f9a7b
2 changed files with 17 additions and 11 deletions
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4
headers/private/print/libprint/Halftone.h
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@ -55,7 +55,7 @@ public:
kHighValueMeansBlack,
kLowValueMeansBlack,
};
Halftone(color_space cs, double gamma = 1.4, DitherType dither_type = kTypeFloydSteinberg);
Halftone(color_space cs, double gamma = 1.4, double min = 0.0, DitherType dither_type = kTypeFloydSteinberg);
~Halftone();
void setPlanes(Planes planes);
void setBlackValue(BlackValue blackValue);
@ -70,7 +70,7 @@ protected:
void setGrayFunction(PFN_gray gray);
void setGrayFunction(GrayFunction grayFunction);
void createGammaTable(double gamma);
void createGammaTable(double gamma, double min);
void initElements(int x, int y, uchar *elements);
uint getDensity(ColorRGB32 c) const;
uchar convertUsingBlackValue(uchar byte) const;

24
src/add-ons/print/drivers/shared/libprint/Halftone.cpp
View File

@ -43,7 +43,7 @@ static uint channel_blue(ColorRGB32 c)
return c.little.blue;
}
Halftone::Halftone(color_space cs, double gamma, DitherType dither_type)
Halftone::Halftone(color_space cs, double gamma, double min, DitherType dither_type)
{
fPixelDepth = color_space2pixel_depth(cs);
fGray = gray;
@ -52,7 +52,7 @@ Halftone::Halftone(color_space cs, double gamma, DitherType dither_type)
initFloydSteinberg();
createGammaTable(gamma);
createGammaTable(gamma, min);
if (dither_type == kTypeFloydSteinberg) {
fDither = &Halftone::ditherFloydSteinberg;
@ -105,12 +105,14 @@ void Halftone::setBlackValue(BlackValue blackValue)
fBlackValue = blackValue;
}
void Halftone::createGammaTable(double gamma)
void Halftone::createGammaTable(double gamma, double min)
{
// gamma = 1.0f / gamma;
uint *g = fGammaTable;
const double kScalingFactor = 255.0 - min;
for (int i = 0; i < kGammaTableSize; i++) {
*g++ = (uint)(pow((double)i / 255.0, gamma) * 256.0);
const double kGammaCorrectedValue = pow((double)i / 255.0, gamma);
const double kTranslatedValue = min + kGammaCorrectedValue * kScalingFactor;
*g++ = (uint)(kTranslatedValue);
}
}
@ -295,7 +297,8 @@ int Halftone::ditherFloydSteinberg(uchar *dst, const uchar* a_src, int x, int y,
}
int* error_table = &fErrorTables[fCurrentPlane][1];
int current_error = 0, error;
int current_error = error_table[0], error;
error_table[0] = 0;
const ColorRGB32 *src = (const ColorRGB32 *)a_src;
uchar cur = 0; // cleared bit means white, set bit means black
for (int x = 0; x < width; x ++, src ++) {
@ -309,10 +312,13 @@ int Halftone::ditherFloydSteinberg(uchar *dst, const uchar* a_src, int x, int y,
error = density - 255;
}
// distribute error
// distribute error using this pattern:
// 0 X 7 (current_error)
// (left) 3 5 1 (right)
// (middle)
int* right = &error_table[x+1];
current_error = *right + 7 * error;
*right = error;
current_error = (*right) + 7 * error;
*right = 1 * error;
int* middle = right - 1;
*middle += 5 * error;