Revert "update SkColor4f::FromColor() to preserve transfer function"

This reverts commit 9e229233a67b36a508d3c753a5b93a022369c5f7.

Reason for revert: See if blocking Android roll

Original change's description:
> update SkColor4f::FromColor() to preserve transfer function
> 
> This kills off some sRGB tables,
> and lots of call sites can now use SkColor4f::FromColor().
> 
> It doesn't seem important to keep this test.
> 
> Change-Id: Ia79ec8ace45e80bbc7a1e33f560f59289e61b2fb
> Reviewed-on: https://skia-review.googlesource.com/141046
> Commit-Queue: Mike Klein <mtklein@chromium.org>
> Reviewed-by: Brian Osman <brianosman@google.com>

TBR=mtklein@chromium.org,brianosman@google.com

Change-Id: I9d76e4ccf8a101853a7404abb33bdab9e0c64c25
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://skia-review.googlesource.com/141181
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>

1 files changed, 28 insertions, 0 deletions

diff --git a/tests/SRGBTest.cpp b/tests/SRGBTest.cpp
index cf8aaa120b..44daeda34a 100644
--- a/tests/SRGBTest.cpp
+++ b/tests/SRGBTest.cpp
@@ -13,6 +13,34 @@
 #include <math.h>
 #include "../src/jumper/SkJumper.h"
 
+static uint8_t linear_to_srgb(float l) {
+    return (uint8_t)sk_linear_to_srgb(Sk4f{l})[0];
+}
+
+DEF_TEST(sk_linear_to_srgb, r) {
+    // 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.
+    uint8_t prev = 0;
+    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);
+        prev = srgb;
+
+        union { float flt; uint32_t bits; } pun = { f };
+        pun.bits++;
+        SkDEBUGCODE(pun.bits += 127);
+        f = pun.flt;
+    }
+}
+
 DEF_TEST(sk_pipeline_srgb_roundtrip, r) {
     uint32_t reds[256];
     for (int i = 0; i < 256; i++) {