00是完全透明(百分百透明)，FF就是完全不透明
透明度 16进制表示 0% FF 1% FC 2% FA 3% F7 4% F5 5% F2 6% F0 7% ED 8% EB 9% E8 10% E6 11% E3 12% E0 13% DE 14% DB 15% D9 16% D6 17% D4 18% D1 19% CF 20% CC 21% C9 22% C7 23% C4 24% C2 25% BF 26% BD 27% BA 28% B8 29% B5 30% B3 31% B0 32% AD 33% AB 34% A8 35% A6 36% A3 37% A1 38% 9E 39% 9C 40% 99 41% 96 42% 94 43% 91 44% 8F 45% 8C 46% 8A 47% 87 48% 85 49% 82 50% 80 51% 7D 52% 7A 53% 78 54% 75 55% 73 56% 70 57% 6E 58% 6B 59% 69 60% 66 61% 63 62% 61 63% 5E 64% 5C 65% 59 66% 57 67% 54 68% 52 69% 4F 70% 4D 71% 4A 72% 47 73% 45 74% 42 75% 40 76% 3D 77% 3B 78% 38 79% 36 80% 33 81% 30 82% 2E 83% 2B 84% 29 85% 26 86% 24 87% 21 88% 1E 89% 1C 90% 1A 91% 17 92% 14 93% 12 94% 0F 95% 0D 96% 0A 97% 07 98% 05 99% 03 100% 00
