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Increase precision of equality checking for color space transfer fns

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BUG=skia:

Change-Id: I7b921d34539c071e63a47fb7151dc1dcdaa08cb3
Reviewed-on: https://skia-review.googlesource.com/9636
Commit-Queue: Brian Osman <brianosman@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
This commit is contained in:
Matt Sarett 2017-03-13 18:21:42 -04:00 committed by Skia Commit-Bot
parent 0727f674bd
commit f85f2a9c93
1 changed files with 25 additions and 19 deletions
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44
src/core/SkColorSpacePriv.h
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@ -58,6 +58,12 @@ static inline bool color_space_almost_equal(float a, float b) {
return SkTAbs(a - b) < 0.01f;
}
// Let's use a stricter version for transfer functions. Worst case, these are encoded
// in ICC format, which offers 16-bits of fractional precision.
static inline bool transfer_fn_almost_equal(float a, float b) {
return SkTAbs(a - b) < 0.001f;
}
static inline bool is_zero_to_one(float v) {
// Because we allow a value just barely larger than 1, the client can use an
// entirely linear transfer function.
@ -115,37 +121,37 @@ static inline bool is_valid_transfer_fn(const SkColorSpaceTransferFn& coeffs) {
}
static inline bool is_almost_srgb(const SkColorSpaceTransferFn& coeffs) {
return color_space_almost_equal(1.0f / 1.055f, coeffs.fA) &&
color_space_almost_equal(0.055f / 1.055f, coeffs.fB) &&
color_space_almost_equal(1.0f / 12.92f, coeffs.fC) &&
color_space_almost_equal(0.04045f, coeffs.fD) &&
color_space_almost_equal(0.00000f, coeffs.fE) &&
color_space_almost_equal(0.00000f, coeffs.fF) &&
color_space_almost_equal(2.40000f, coeffs.fG);
return transfer_fn_almost_equal(1.0f / 1.055f, coeffs.fA) &&
transfer_fn_almost_equal(0.055f / 1.055f, coeffs.fB) &&
transfer_fn_almost_equal(1.0f / 12.92f, coeffs.fC) &&
transfer_fn_almost_equal(0.04045f, coeffs.fD) &&
transfer_fn_almost_equal(0.00000f, coeffs.fE) &&
transfer_fn_almost_equal(0.00000f, coeffs.fF) &&
transfer_fn_almost_equal(2.40000f, coeffs.fG);
}
static inline bool is_almost_2dot2(const SkColorSpaceTransferFn& coeffs) {
return color_space_almost_equal(1.0f, coeffs.fA) &&
color_space_almost_equal(0.0f, coeffs.fB) &&
color_space_almost_equal(0.0f, coeffs.fE) &&
color_space_almost_equal(2.2f, coeffs.fG) &&
return transfer_fn_almost_equal(1.0f, coeffs.fA) &&
transfer_fn_almost_equal(0.0f, coeffs.fB) &&
transfer_fn_almost_equal(0.0f, coeffs.fE) &&
transfer_fn_almost_equal(2.2f, coeffs.fG) &&
coeffs.fD <= 0.0f;
}
static inline bool is_almost_linear(const SkColorSpaceTransferFn& coeffs) {
// OutputVal = InputVal ^ 1.0f
const bool linearExp =
color_space_almost_equal(1.0f, coeffs.fA) &&
color_space_almost_equal(0.0f, coeffs.fB) &&
color_space_almost_equal(0.0f, coeffs.fE) &&
color_space_almost_equal(1.0f, coeffs.fG) &&
coeffs.fD <= 0.0f;
transfer_fn_almost_equal(1.0f, coeffs.fA) &&
transfer_fn_almost_equal(0.0f, coeffs.fB) &&
transfer_fn_almost_equal(0.0f, coeffs.fE) &&
transfer_fn_almost_equal(1.0f, coeffs.fG) &&
coeffs.fD <= 0.0f;
// OutputVal = 1.0f * InputVal
const bool linearFn =
color_space_almost_equal(1.0f, coeffs.fC) &&
color_space_almost_equal(0.0f, coeffs.fF) &&
coeffs.fD >= 1.0f;
transfer_fn_almost_equal(1.0f, coeffs.fC) &&
transfer_fn_almost_equal(0.0f, coeffs.fF) &&
coeffs.fD >= 1.0f;
return linearExp || linearFn;
}