Tune linear->sRGB constants to round-trip all bytes.
I basically just ran a big 5-deep for-loop over the five constants here.
This is the first set of coefficients I found that round trips all bytes.
I suspect there are many such sets.
BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2162063003
CQ_INCLUDE_TRYBOTS=master.client.skia:Test-Ubuntu-GCC-GCE-CPU-AVX2-x86_64-Release-SKNX_NO_SIMD-Trybot
Review-Url: https://codereview.chromium.org/2162063003
diff --git a/tests/SRGBTest.cpp b/tests/SRGBTest.cpp
index 65bfc59..43ec027 100644
--- a/tests/SRGBTest.cpp
+++ b/tests/SRGBTest.cpp
@@ -11,28 +11,24 @@
#include <math.h>
static uint8_t linear_to_srgb(float l) {
- // Round float to int, truncate that to uint8_t.
- return (uint8_t)Sk4f_round( sk_linear_to_srgb(Sk4f{l}) )[0];
+ return (uint8_t)sk_linear_to_srgb(Sk4f{l})[0];
}
DEF_TEST(sk_linear_to_srgb, r) {
- // Should map 0 -> 0 and 1 -> 1.
- REPORTER_ASSERT(r, 0 == linear_to_srgb(0.0f));
- REPORTER_ASSERT(r, 255 == linear_to_srgb(1.0f));
+ // All bytes should round trip.
+ for (int i = 0; i < 256; i++) {
+ int actual = linear_to_srgb(sk_linear_from_srgb[i]);
+ if (i != actual) {
+ ERRORF(r, "%d -> %d\n", i, actual);
+ }
+ }
// Should be monotonic between 0 and 1.
- // We don't bother checking denorm values.
- int tolerated_regressions = 0;
-#if defined(SK_ARM_HAS_NEON)
- // Values around 0.166016 are usually 72 but drop briefly (41 floats) down to 71.
- tolerated_regressions = 1;
-#endif
uint8_t prev = 0;
- for (float f = FLT_MIN; f <= 1.0f; ) {
+ for (float f = FLT_MIN; f <= 1.0f; ) { // We don't bother checking denorm values.
uint8_t srgb = linear_to_srgb(f);
- REPORTER_ASSERT(r, srgb >= prev || tolerated_regressions > 0);
- if (srgb < prev) { tolerated_regressions--; }
+ REPORTER_ASSERT(r, srgb >= prev);
prev = srgb;
union { float flt; uint32_t bits; } pun = { f };