| |
| /* |
| * Copyright 2011 Google Inc. |
| * |
| * Use of this source code is governed by a BSD-style license that can be |
| * found in the LICENSE file. |
| */ |
| #include "Test.h" |
| #include "SkColorPriv.h" |
| #include "SkXfermode.h" |
| |
| // our std SkAlpha255To256 |
| static int test_srcover0(unsigned dst, unsigned alpha) { |
| return alpha + SkAlphaMul(dst, SkAlpha255To256(255 - alpha)); |
| } |
| |
| // faster hack +1 |
| static int test_srcover1(unsigned dst, unsigned alpha) { |
| return alpha + SkAlphaMul(dst, 256 - alpha); |
| } |
| |
| // slower "correct" |
| static int test_srcover2(unsigned dst, unsigned alpha) { |
| return alpha + SkMulDiv255Round(dst, 255 - alpha); |
| } |
| |
| static void test_srcover_hack(skiatest::Reporter* reporter) { |
| /* Here's the idea. Can we ensure that when we blend on top of an opaque |
| dst, that the result always stay's opaque (i.e. exactly 255)? |
| */ |
| |
| unsigned i; |
| int opaqueCounter0 = 0; |
| int opaqueCounter1 = 0; |
| int opaqueCounter2 = 0; |
| for (i = 0; i <= 255; i++) { |
| unsigned result0 = test_srcover0(0xFF, i); |
| unsigned result1 = test_srcover1(0xFF, i); |
| unsigned result2 = test_srcover2(0xFF, i); |
| opaqueCounter0 += (result0 == 0xFF); |
| opaqueCounter1 += (result1 == 0xFF); |
| opaqueCounter2 += (result2 == 0xFF); |
| } |
| #if 0 |
| SkDebugf("---- opaque test: [%d %d %d]\n", |
| opaqueCounter0, opaqueCounter1, opaqueCounter2); |
| #endif |
| // we acknowledge that technique0 does not always return opaque |
| REPORTER_ASSERT(reporter, opaqueCounter0 == 256); |
| REPORTER_ASSERT(reporter, opaqueCounter1 == 256); |
| REPORTER_ASSERT(reporter, opaqueCounter2 == 256); |
| |
| // Now ensure that we never over/underflow a byte |
| for (i = 0; i <= 255; i++) { |
| for (unsigned dst = 0; dst <= 255; dst++) { |
| unsigned r0 = test_srcover0(dst, i); |
| unsigned r1 = test_srcover1(dst, i); |
| unsigned r2 = test_srcover2(dst, i); |
| unsigned max = SkMax32(dst, i); |
| // ignore the known failure |
| if (dst != 255) { |
| REPORTER_ASSERT(reporter, r0 <= 255 && r0 >= max); |
| } |
| REPORTER_ASSERT(reporter, r1 <= 255 && r1 >= max); |
| REPORTER_ASSERT(reporter, r2 <= 255 && r2 >= max); |
| |
| #if 0 |
| // this shows where r1 (faster) differs from r2 (more exact) |
| if (r1 != r2) { |
| SkDebugf("--- dst=%d i=%d r1=%d r2=%d exact=%g\n", |
| dst, i, r1, r2, i + dst - dst*i/255.0f); |
| } |
| #endif |
| } |
| } |
| } |
| |
| #include "TestClassDef.h" |
| DEFINE_TESTCLASS("SrcOver", SrcOverTestClass, test_srcover_hack) |