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Diffstat (limited to 'src/core/SkColorSpaceXform.cpp')
-rw-r--r--src/core/SkColorSpaceXform.cpp200
1 files changed, 181 insertions, 19 deletions
diff --git a/src/core/SkColorSpaceXform.cpp b/src/core/SkColorSpaceXform.cpp
index 473e715353..216e9931ba 100644
--- a/src/core/SkColorSpaceXform.cpp
+++ b/src/core/SkColorSpaceXform.cpp
@@ -9,8 +9,8 @@
#include "SkColorSpace_Base.h"
#include "SkColorSpaceXform.h"
-bool compute_gamut_xform(SkMatrix44* srcToDst, const SkMatrix44& srcToXYZ,
- const SkMatrix44& dstToXYZ) {
+static inline bool compute_gamut_xform(SkMatrix44* srcToDst, const SkMatrix44& srcToXYZ,
+ const SkMatrix44& dstToXYZ) {
if (!dstToXYZ.invert(srcToDst)) {
return false;
}
@@ -22,15 +22,21 @@ bool compute_gamut_xform(SkMatrix44* srcToDst, const SkMatrix44& srcToXYZ,
std::unique_ptr<SkColorSpaceXform> SkColorSpaceXform::New(const sk_sp<SkColorSpace>& srcSpace,
const sk_sp<SkColorSpace>& dstSpace) {
if (!srcSpace || !dstSpace) {
+ // Invalid input
return nullptr;
}
- if (as_CSB(srcSpace)->gammas()->isValues() && as_CSB(dstSpace)->gammas()->isValues()) {
- SkMatrix44 srcToDst(SkMatrix44::kUninitialized_Constructor);
- if (!compute_gamut_xform(&srcToDst, srcSpace->xyz(), dstSpace->xyz())) {
- return nullptr;
- }
+ if (as_CSB(srcSpace)->colorLUT() || as_CSB(dstSpace)->colorLUT()) {
+ // Unimplemented
+ return nullptr;
+ }
+ SkMatrix44 srcToDst(SkMatrix44::kUninitialized_Constructor);
+ if (!compute_gamut_xform(&srcToDst, srcSpace->xyz(), dstSpace->xyz())) {
+ return nullptr;
+ }
+
+ if (as_CSB(srcSpace)->gammas()->isValues() && as_CSB(dstSpace)->gammas()->isValues()) {
float srcGammas[3];
float dstGammas[3];
srcGammas[0] = as_CSB(srcSpace)->gammas()->fRed.fValue;
@@ -44,21 +50,17 @@ std::unique_ptr<SkColorSpaceXform> SkColorSpaceXform::New(const sk_sp<SkColorSpa
new SkGammaByValueXform(srcGammas, srcToDst, dstGammas));
}
- // Unimplemeted
- return nullptr;
+ return std::unique_ptr<SkColorSpaceXform>(
+ new SkDefaultXform(as_CSB(srcSpace)->gammas(), srcToDst, as_CSB(dstSpace)->gammas()));
}
///////////////////////////////////////////////////////////////////////////////////////////////////
-SkGammaByValueXform::SkGammaByValueXform(float srcGammas[3], const SkMatrix44& srcToDst,
- float dstGammas[3])
- : fSrcToDst(srcToDst)
-{
- memcpy(fSrcGammas, srcGammas, 3 * sizeof(float));
- memcpy(fDstGammas, dstGammas, 3 * sizeof(float));
+static inline float byte_to_float(uint8_t v) {
+ return ((float) v) * (1.0f / 255.0f);
}
-static uint8_t clamp_float_to_byte(float v) {
+static inline uint8_t clamp_float_to_byte(float v) {
v = v * 255.0f;
if (v > 255.0f) {
return 255;
@@ -69,12 +71,22 @@ static uint8_t clamp_float_to_byte(float v) {
}
}
+///////////////////////////////////////////////////////////////////////////////////////////////////
+
+SkGammaByValueXform::SkGammaByValueXform(float srcGammas[3], const SkMatrix44& srcToDst,
+ float dstGammas[3])
+ : fSrcToDst(srcToDst)
+{
+ memcpy(fSrcGammas, srcGammas, 3 * sizeof(float));
+ memcpy(fDstGammas, dstGammas, 3 * sizeof(float));
+}
+
void SkGammaByValueXform::xform_RGBA_8888(uint32_t* dst, const uint32_t* src, uint32_t len) const {
while (len-- > 0) {
float srcFloats[3];
- srcFloats[0] = ((*src >> 0) & 0xFF) * (1.0f / 255.0f);
- srcFloats[1] = ((*src >> 8) & 0xFF) * (1.0f / 255.0f);
- srcFloats[2] = ((*src >> 16) & 0xFF) * (1.0f / 255.0f);
+ srcFloats[0] = byte_to_float((*src >> 0) & 0xFF);
+ srcFloats[1] = byte_to_float((*src >> 8) & 0xFF);
+ srcFloats[2] = byte_to_float((*src >> 16) & 0xFF);
// Convert to linear.
srcFloats[0] = pow(srcFloats[0], fSrcGammas[0]);
@@ -107,3 +119,153 @@ void SkGammaByValueXform::xform_RGBA_8888(uint32_t* dst, const uint32_t* src, ui
src++;
}
}
+
+///////////////////////////////////////////////////////////////////////////////////////////////////
+
+// Interpolating lookup in a variably sized table.
+static inline float interp_lut(uint8_t byte, float* table, size_t tableSize) {
+ float index = byte_to_float(byte) * (tableSize - 1);
+ float diff = index - sk_float_floor2int(index);
+ return table[(int) sk_float_floor2int(index)] * (1.0f - diff) +
+ table[(int) sk_float_ceil2int(index)] * diff;
+}
+
+// Inverse table lookup. Ex: what index corresponds to the input value? This will
+// have strange results when the table is non-increasing. But any sane gamma
+// function will be increasing.
+// FIXME (msarett):
+// This is a placeholder implementation for inverting table gammas. First, I need to
+// verify if there are actually destination profiles that require this functionality.
+// Next, there are certainly faster and more robust approaches to solving this problem.
+// The LUT based approach in QCMS would be a good place to start.
+static inline float interp_lut_inv(float input, float* table, size_t tableSize) {
+ if (input <= table[0]) {
+ return table[0];
+ } else if (input >= table[tableSize - 1]) {
+ return 1.0f;
+ }
+
+ for (uint32_t i = 1; i < tableSize; i++) {
+ if (table[i] >= input) {
+ // We are guaranteed that input is greater than table[i - 1].
+ float diff = input - table[i - 1];
+ float distance = table[i] - table[i - 1];
+ float index = (i - 1) + diff / distance;
+ return index / (tableSize - 1);
+ }
+ }
+
+ // Should be unreachable, since we'll return before the loop if input is
+ // larger than the last entry.
+ SkASSERT(false);
+ return 0.0f;
+}
+
+SkDefaultXform::SkDefaultXform(const sk_sp<SkGammas>& srcGammas, const SkMatrix44& srcToDst,
+ const sk_sp<SkGammas>& dstGammas)
+ : fSrcGammas(srcGammas)
+ , fSrcToDst(srcToDst)
+ , fDstGammas(dstGammas)
+{}
+
+void SkDefaultXform::xform_RGBA_8888(uint32_t* dst, const uint32_t* src, uint32_t len) const {
+ while (len-- > 0) {
+ // Convert to linear.
+ // FIXME (msarett):
+ // Rather than support three different strategies of transforming gamma, QCMS
+ // builds a 256 entry float lookup table from the gamma info. This handles
+ // the gamma transform and the conversion from bytes to floats. This may
+ // be simpler and faster than our current approach.
+ float srcFloats[3];
+ for (int i = 0; i < 3; i++) {
+ const SkGammaCurve& gamma = (*fSrcGammas)[i];
+ uint8_t byte = (*src >> (8 * i)) & 0xFF;
+ if (gamma.isValue()) {
+ srcFloats[i] = pow(byte_to_float(byte), gamma.fValue);
+ } else if (gamma.isTable()) {
+ srcFloats[i] = interp_lut(byte, gamma.fTable.get(), gamma.fTableSize);
+ } else {
+ SkASSERT(gamma.isParametric());
+ float component = byte_to_float(byte);
+ if (component < gamma.fD) {
+ // Y = E * X + F
+ srcFloats[i] = gamma.fE * component + gamma.fF;
+ } else {
+ // Y = (A * X + B)^G + C
+ srcFloats[i] = pow(gamma.fA * component + gamma.fB, gamma.fG) + gamma.fC;
+ }
+ }
+ }
+
+ // Convert to dst gamut.
+ float dstFloats[3];
+ dstFloats[0] = srcFloats[0] * fSrcToDst.getFloat(0, 0) +
+ srcFloats[1] * fSrcToDst.getFloat(1, 0) +
+ srcFloats[2] * fSrcToDst.getFloat(2, 0) + fSrcToDst.getFloat(3, 0);
+ dstFloats[1] = srcFloats[0] * fSrcToDst.getFloat(0, 1) +
+ srcFloats[1] * fSrcToDst.getFloat(1, 1) +
+ srcFloats[2] * fSrcToDst.getFloat(2, 1) + fSrcToDst.getFloat(3, 1);
+ dstFloats[2] = srcFloats[0] * fSrcToDst.getFloat(0, 2) +
+ srcFloats[1] * fSrcToDst.getFloat(1, 2) +
+ srcFloats[2] * fSrcToDst.getFloat(2, 2) + fSrcToDst.getFloat(3, 2);
+
+ // Convert to dst gamma.
+ // FIXME (msarett):
+ // Rather than support three different strategies of transforming inverse gamma,
+ // QCMS builds a large float lookup table from the gamma info. Is this faster or
+ // better than our approach?
+ for (int i = 0; i < 3; i++) {
+ const SkGammaCurve& gamma = (*fDstGammas)[i];
+ if (gamma.isValue()) {
+ dstFloats[i] = pow(dstFloats[i], 1.0f / gamma.fValue);
+ } else if (gamma.isTable()) {
+ // FIXME (msarett):
+ // An inverse table lookup is particularly strange and non-optimal.
+ dstFloats[i] = interp_lut_inv(dstFloats[i], gamma.fTable.get(), gamma.fTableSize);
+ } else {
+ SkASSERT(gamma.isParametric());
+ // FIXME (msarett):
+ // This is a placeholder implementation for inverting parametric gammas.
+ // First, I need to verify if there are actually destination profiles that
+ // require this functionality. Next, I need to explore other possibilities
+ // for this implementation. The LUT based approach in QCMS would be a good
+ // place to start.
+
+ // We need to take the inverse of a piecewise function. Assume that
+ // the gamma function is continuous, or this won't make much sense
+ // anyway.
+ // Plug in |fD| to the first equation to calculate the new piecewise
+ // interval. Then simply use the inverse of the original functions.
+ float interval = gamma.fE * gamma.fD + gamma.fF;
+ if (dstFloats[i] < interval) {
+ // X = (Y - F) / E
+ if (0.0f == gamma.fE) {
+ // The gamma curve for this segment is constant, so the inverse
+ // is undefined.
+ dstFloats[i] = 0.0f;
+ } else {
+ dstFloats[i] = (dstFloats[i] - gamma.fF) / gamma.fE;
+ }
+ } else {
+ // X = ((Y - C)^(1 / G) - B) / A
+ if (0.0f == gamma.fA || 0.0f == gamma.fG) {
+ // The gamma curve for this segment is constant, so the inverse
+ // is undefined.
+ dstFloats[i] = 0.0f;
+ } else {
+ dstFloats[i] = (pow(dstFloats[i] - gamma.fC, 1.0f / gamma.fG) - gamma.fB)
+ / gamma.fA;
+ }
+ }
+ }
+ }
+
+ *dst = SkPackARGB32NoCheck(((*src >> 24) & 0xFF),
+ clamp_float_to_byte(dstFloats[0]),
+ clamp_float_to_byte(dstFloats[1]),
+ clamp_float_to_byte(dstFloats[2]));
+
+ dst++;
+ src++;
+ }
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-07-29 12:45:53 +0000