Align SkLumaColorFilter with the spec.

The spec requires the resulting RGB channels for LuminanceToAlpha to be
0 (and not just scaled by the luminance value</facepalm>):

  | R' |     |      0        0        0  0  0 |   | R |
  | G' |     |      0        0        0  0  0 |   | G |
  | B' |  =  |      0        0        0  0  0 | * | B |
  | A' |     | 0.2125   0.7154   0.0721  0  0 |   | A |
  | 1  |     |      0        0        0  0  1 |   | 1 |

(http://www.w3.org/TR/2011/REC-SVG11-20110816/filters.html#feColorMatrixElement)

This doesn't affect luminance masking (which depends only on the
resulting alpha channel), but other color filter users may care
about all color components.

R=bsalomon@google.com, reed@google.com, robertphillips@google.com

Author: fmalita@chromium.org

Review URL: https://codereview.chromium.org/26467003

git-svn-id: http://skia.googlecode.com/svn/trunk@11713 2bbb7eff-a529-9590-31e7-b0007b416f81

1 files changed, 9 insertions, 6 deletions

diff --git a/tests/ColorFilterTest.cpp b/tests/ColorFilterTest.cpp
index b333ad68f0..8c96d752fb 100644
--- a/tests/ColorFilterTest.cpp
+++ b/tests/ColorFilterTest.cpp
@@ -101,11 +101,14 @@ static void test_lumaColorFilter(skiatest::Reporter* reporter) {
     SkPMColor in, out;
     SkAutoTUnref<SkColorFilter> lf(SkLumaColorFilter::Create());
 
-    // Applying luma to white is a nop (luminance(white) == 1.0)
+    // Applying luma to white produces black with the same transparency.
     for (unsigned i = 0; i < 256; ++i) {
         in = SkPackARGB32(i, i, i, i);
         lf->filterSpan(&in, 1, &out);
-        REPORTER_ASSERT(reporter, out == in);
+        REPORTER_ASSERT(reporter, SkGetPackedA32(out) == i);
+        REPORTER_ASSERT(reporter, SkGetPackedR32(out) == 0);
+        REPORTER_ASSERT(reporter, SkGetPackedG32(out) == 0);
+        REPORTER_ASSERT(reporter, SkGetPackedB32(out) == 0);
     }
 
     // Applying luma to black yields transparent black (luminance(black) == 0)
@@ -115,15 +118,15 @@ static void test_lumaColorFilter(skiatest::Reporter* reporter) {
         REPORTER_ASSERT(reporter, out == SK_ColorTRANSPARENT);
     }
 
-    // For general colors, a luma filter has an attenuating effect.
+    // For general colors, a luma filter generates black with an attenuated alpha channel.
     for (unsigned i = 1; i < 256; ++i) {
         in = SkPackARGB32(i, i, i / 2, i / 3);
         lf->filterSpan(&in, 1, &out);
         REPORTER_ASSERT(reporter, out != in);
         REPORTER_ASSERT(reporter, SkGetPackedA32(out) <= i);
-        REPORTER_ASSERT(reporter, SkGetPackedR32(out) <= i);
-        REPORTER_ASSERT(reporter, SkGetPackedG32(out) <= i / 2);
-        REPORTER_ASSERT(reporter, SkGetPackedB32(out) <= i / 3);
+        REPORTER_ASSERT(reporter, SkGetPackedR32(out) == 0);
+        REPORTER_ASSERT(reporter, SkGetPackedG32(out) == 0);
+        REPORTER_ASSERT(reporter, SkGetPackedB32(out) == 0);
     }
 }