1/* libs/pixelflinger/col32cb16blend.S 2 * 3 * Copyright (C) 2009 The Android Open Source Project 4 * 5 * Licensed under the Apache License, Version 2.0 (the "License"); 6 * you may not use this file except in compliance with the License. 7 * You may obtain a copy of the License at 8 * 9 * http://www.apache.org/licenses/LICENSE-2.0 10 * 11 * Unless required by applicable law or agreed to in writing, software 12 * distributed under the License is distributed on an "AS IS" BASIS, 13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 14 * See the License for the specific language governing permissions and 15 * limitations under the License. 16 */ 17 18 .text 19 .align 20 21 .global scanline_col32cb16blend_arm 22 23// 24// This function alpha blends a fixed color into a destination scanline, using 25// the formula: 26// 27// d = s + (((a + (a >> 7)) * d) >> 8) 28// 29// where d is the destination pixel, 30// s is the source color, 31// a is the alpha channel of the source color. 32// 33 34// r0 = destination buffer pointer 35// r1 = color value 36// r2 = count 37 38 39scanline_col32cb16blend_arm: 40 push {r4-r10, lr} // stack ARM regs 41 42 mov r5, r1, lsr #24 // shift down alpha 43 mov r9, #0xff // create mask 44 add r5, r5, r5, lsr #7 // add in top bit 45 rsb r5, r5, #256 // invert alpha 46 and r10, r1, #0xff // extract red 47 and r12, r9, r1, lsr #8 // extract green 48 and r4, r9, r1, lsr #16 // extract blue 49 mov r10, r10, lsl #5 // prescale red 50 mov r12, r12, lsl #6 // prescale green 51 mov r4, r4, lsl #5 // prescale blue 52 mov r9, r9, lsr #2 // create dest green mask 53 541: 55 ldrh r8, [r0] // load dest pixel 56 subs r2, r2, #1 // decrement loop counter 57 mov r6, r8, lsr #11 // extract dest red 58 and r7, r9, r8, lsr #5 // extract dest green 59 and r8, r8, #0x1f // extract dest blue 60 61 smlabb r6, r6, r5, r10 // dest red * alpha + src red 62 smlabb r7, r7, r5, r12 // dest green * alpha + src green 63 smlabb r8, r8, r5, r4 // dest blue * alpha + src blue 64 65 mov r6, r6, lsr #8 // shift down red 66 mov r7, r7, lsr #8 // shift down green 67 mov r6, r6, lsl #11 // shift red into 565 68 orr r6, r7, lsl #5 // shift green into 565 69 orr r6, r8, lsr #8 // shift blue into 565 70 71 strh r6, [r0], #2 // store pixel to dest, update ptr 72 bne 1b // if count != 0, loop 73 74 pop {r4-r10, pc} // return 75 76 77 78