1 /* 2 * Copyright 2011 Google Inc. 3 * 4 * Use of this source code is governed by a BSD-style license that can be 5 * found in the LICENSE file. 6 */ 7 8 #include "SkColorPriv.h" 9 #include "SkXfermode.h" 10 #include "Test.h" 11 12 // our std SkAlpha255To256 13 static int test_srcover0(unsigned dst, unsigned alpha) { 14 return alpha + SkAlphaMul(dst, SkAlpha255To256(255 - alpha)); 15 } 16 17 // faster hack +1 18 static int test_srcover1(unsigned dst, unsigned alpha) { 19 return alpha + SkAlphaMul(dst, 256 - alpha); 20 } 21 22 // slower "correct" 23 static int test_srcover2(unsigned dst, unsigned alpha) { 24 return alpha + SkMulDiv255Round(dst, 255 - alpha); 25 } 26 27 DEF_TEST(SrcOver, reporter) { 28 /* Here's the idea. Can we ensure that when we blend on top of an opaque 29 dst, that the result always stay's opaque (i.e. exactly 255)? 30 */ 31 32 unsigned i; 33 int opaqueCounter0 = 0; 34 int opaqueCounter1 = 0; 35 int opaqueCounter2 = 0; 36 for (i = 0; i <= 255; i++) { 37 unsigned result0 = test_srcover0(0xFF, i); 38 unsigned result1 = test_srcover1(0xFF, i); 39 unsigned result2 = test_srcover2(0xFF, i); 40 opaqueCounter0 += (result0 == 0xFF); 41 opaqueCounter1 += (result1 == 0xFF); 42 opaqueCounter2 += (result2 == 0xFF); 43 } 44 #if 0 45 INFOF(reporter, "---- opaque test: [%d %d %d]\n", 46 opaqueCounter0, opaqueCounter1, opaqueCounter2); 47 #endif 48 // we acknowledge that technique0 does not always return opaque 49 REPORTER_ASSERT(reporter, opaqueCounter0 == 256); 50 REPORTER_ASSERT(reporter, opaqueCounter1 == 256); 51 REPORTER_ASSERT(reporter, opaqueCounter2 == 256); 52 53 // Now ensure that we never over/underflow a byte 54 for (i = 0; i <= 255; i++) { 55 for (unsigned dst = 0; dst <= 255; dst++) { 56 unsigned r0 = test_srcover0(dst, i); 57 unsigned r1 = test_srcover1(dst, i); 58 unsigned r2 = test_srcover2(dst, i); 59 unsigned max = SkMax32(dst, i); 60 // ignore the known failure 61 if (dst != 255) { 62 REPORTER_ASSERT(reporter, r0 <= 255 && r0 >= max); 63 } 64 REPORTER_ASSERT(reporter, r1 <= 255 && r1 >= max); 65 REPORTER_ASSERT(reporter, r2 <= 255 && r2 >= max); 66 67 #if 0 68 // this shows where r1 (faster) differs from r2 (more exact) 69 if (r1 != r2) { 70 INFOF(reporter, "--- dst=%d i=%d r1=%d r2=%d exact=%g\n", 71 dst, i, r1, r2, i + dst - dst*i/255.0f); 72 } 73 #endif 74 } 75 } 76 } 77
