/* Generate Type 4 function code to map t=[0,1) to the passed gradient,
clamping at the edges of the range. The generated code will be of the form:
if (t < 0) {
return colorData[0][r,g,b];
} else {
if (t < info.fColorOffsets[1]) {
return linearinterpolation(colorData[0][r,g,b],
colorData[1][r,g,b]);
} else {
if (t < info.fColorOffsets[2]) {
return linearinterpolation(colorData[1][r,g,b],
colorData[2][r,g,b]);
} else {
... } else {
return colorData[info.fColorCount - 1][r,g,b];
}
...
}
}
*/
static void gradientFunctionCode(const SkShader::GradientInfo& info,
SkString* result) {
/* We want to linearly interpolate from the previous color to the next.
Scale the colors from 0..255 to 0..1 and determine the multipliers
for interpolation.
C{r,g,b}(t, section) = t - offset_(section-1) + t * Multiplier{r,g,b}.
*/
static const int kColorComponents = 3;
typedef SkScalar ColorTuple[kColorComponents];
SkAutoSTMalloc<4, ColorTuple> colorDataAlloc(info.fColorCount);
ColorTuple *colorData = colorDataAlloc.get();
const SkScalar scale = SkScalarInvert(SkIntToScalar(255));
for (int i = 0; i < info.fColorCount; i++) {
colorData[i][0] = SkScalarMul(SkColorGetR(info.fColors[i]), scale);
colorData[i][1] = SkScalarMul(SkColorGetG(info.fColors[i]), scale);
colorData[i][2] = SkScalarMul(SkColorGetB(info.fColors[i]), scale);
}
// Clamp the initial color.
result->append("dup 0 le {pop ");
result->appendScalar(colorData[0][0]);
result->append(" ");
result->appendScalar(colorData[0][1]);
result->append(" ");
result->appendScalar(colorData[0][2]);
result->append(" }\n");
// The gradient colors.
int gradients = 0;
for (int i = 1 ; i < info.fColorCount; i++) {
if (info.fColorOffsets[i] == info.fColorOffsets[i - 1]) {
continue;
}
gradients++;
result->append("{dup ");
result->appendScalar(info.fColorOffsets[i]);
result->append(" le {");
if (info.fColorOffsets[i - 1] != 0) {
result->appendScalar(info.fColorOffsets[i - 1]);
result->append(" sub\n");
}
interpolateColorCode(info.fColorOffsets[i] - info.fColorOffsets[i - 1],
colorData[i], colorData[i - 1], result);
result->append("}\n");
}
// Clamp the final color.
result->append("{pop ");
result->appendScalar(colorData[info.fColorCount - 1][0]);
result->append(" ");
result->appendScalar(colorData[info.fColorCount - 1][1]);
result->append(" ");
result->appendScalar(colorData[info.fColorCount - 1][2]);
for (int i = 0 ; i < gradients + 1; i++) {
result->append("} ifelse\n");
}
}
/* Generate Type 4 function code to map t=[0,1) to the passed gradient,
clamping at the edges of the range. The generated code will be of the form:
if (t < 0) {
return colorData[0][r,g,b];
} else {
if (t < info.fColorOffsets[1]) {
return linearinterpolation(colorData[0][r,g,b],
colorData[1][r,g,b]);
} else {
if (t < info.fColorOffsets[2]) {
return linearinterpolation(colorData[1][r,g,b],
colorData[2][r,g,b]);
} else {
... } else {
return colorData[info.fColorCount - 1][r,g,b];
}
...
}
}
*/
static void gradient_function_code(const SkShader::GradientInfo& info,
SkDynamicMemoryWStream* result) {
/* We want to linearly interpolate from the previous color to the next.
Scale the colors from 0..255 to 0..1 and determine the multipliers
for interpolation.
C{r,g,b}(t, section) = t - offset_(section-1) + t * Multiplier{r,g,b}.
*/
SkAutoSTMalloc<4, ColorTuple> colorDataAlloc(info.fColorCount);
ColorTuple *colorData = colorDataAlloc.get();
for (int i = 0; i < info.fColorCount; i++) {
colorData[i][0] = SkColorGetR(info.fColors[i]);
colorData[i][1] = SkColorGetG(info.fColors[i]);
colorData[i][2] = SkColorGetB(info.fColors[i]);
}
// Clamp the initial color.
result->writeText("dup 0 le {pop ");
SkPDFUtils::AppendColorComponent(colorData[0][0], result);
result->writeText(" ");
SkPDFUtils::AppendColorComponent(colorData[0][1], result);
result->writeText(" ");
SkPDFUtils::AppendColorComponent(colorData[0][2], result);
result->writeText(" }\n");
// The gradient colors.
int gradients = 0;
for (int i = 1 ; i < info.fColorCount; i++) {
if (info.fColorOffsets[i] == info.fColorOffsets[i - 1]) {
continue;
}
gradients++;
result->writeText("{dup ");
SkPDFUtils::AppendScalar(info.fColorOffsets[i], result);
result->writeText(" le {");
if (info.fColorOffsets[i - 1] != 0) {
SkPDFUtils::AppendScalar(info.fColorOffsets[i - 1], result);
result->writeText(" sub\n");
}
interpolate_color_code(info.fColorOffsets[i] - info.fColorOffsets[i - 1],
colorData[i], colorData[i - 1], result);
result->writeText("}\n");
}
// Clamp the final color.
result->writeText("{pop ");
SkPDFUtils::AppendColorComponent(colorData[info.fColorCount - 1][0], result);
result->writeText(" ");
SkPDFUtils::AppendColorComponent(colorData[info.fColorCount - 1][1], result);
result->writeText(" ");
SkPDFUtils::AppendColorComponent(colorData[info.fColorCount - 1][2], result);
for (int i = 0 ; i < gradients + 1; i++) {
result->writeText("} ifelse\n");
}
}
static std::unique_ptr<SkPDFDict> gradientStitchCode(const SkShader::GradientInfo& info) {
auto retval = SkPDFMakeDict();
// normalize color stops
int colorCount = info.fColorCount;
std::vector<SkColor> colors(info.fColors, info.fColors + colorCount);
std::vector<SkScalar> colorOffsets(info.fColorOffsets, info.fColorOffsets + colorCount);
int i = 1;
while (i < colorCount - 1) {
// ensure stops are in order
if (colorOffsets[i - 1] > colorOffsets[i]) {
colorOffsets[i] = colorOffsets[i - 1];
}
// remove points that are between 2 coincident points
if ((colorOffsets[i - 1] == colorOffsets[i]) && (colorOffsets[i] == colorOffsets[i + 1])) {
colorCount -= 1;
colors.erase(colors.begin() + i);
colorOffsets.erase(colorOffsets.begin() + i);
} else {
i++;
}
}
// find coincident points and slightly move them over
for (i = 1; i < colorCount - 1; i++) {
if (colorOffsets[i - 1] == colorOffsets[i]) {
colorOffsets[i] += 0.00001f;
}
}
// check if last 2 stops coincide
if (colorOffsets[i - 1] == colorOffsets[i]) {
colorOffsets[i - 1] -= 0.00001f;
}
SkAutoSTMalloc<4, ColorTuple> colorDataAlloc(colorCount);
ColorTuple *colorData = colorDataAlloc.get();
for (int i = 0; i < colorCount; i++) {
colorData[i][0] = SkColorGetR(colors[i]);
colorData[i][1] = SkColorGetG(colors[i]);
colorData[i][2] = SkColorGetB(colors[i]);
}
// no need for a stitch function if there are only 2 stops.
if (colorCount == 2)
return createInterpolationFunction(colorData[0], colorData[1]);
auto encode = SkPDFMakeArray();
auto bounds = SkPDFMakeArray();
auto functions = SkPDFMakeArray();
retval->insertObject("Domain", SkPDFMakeArray(0, 1));
retval->insertInt("FunctionType", 3);
for (int i = 1; i < colorCount; i++) {
if (i > 1) {
bounds->appendScalar(colorOffsets[i-1]);
}
encode->appendScalar(0);
encode->appendScalar(1.0f);
functions->appendObject(createInterpolationFunction(colorData[i-1], colorData[i]));
}
retval->insertObject("Encode", std::move(encode));
retval->insertObject("Bounds", std::move(bounds));
retval->insertObject("Functions", std::move(functions));
return retval;
}
