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- /*
- * 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 "include/private/SkColorData.h"
- #include "tests/Test.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);
- }
- DEF_TEST(SrcOver, 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
- INFOF(reporter, "---- 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) {
- INFOF(reporter, "--- dst=%d i=%d r1=%d r2=%d exact=%g\n",
- dst, i, r1, r2, i + dst - dst*i/255.0f);
- }
- #endif
- }
- }
- }
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