/* libs/pixelflinger/col32cb16blend.S
*
* Copyright (C) 2009 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
.text
.align
.global scanline_col32cb16blend_arm
//
// This function alpha blends a fixed color into a destination scanline, using
// the formula:
//
// d = s + (((a + (a >> 7)) * d) >> 8)
//
// where d is the destination pixel,
// s is the source color,
// a is the alpha channel of the source color.
//
// r0 = destination buffer pointer
// r1 = color value
// r2 = count
scanline_col32cb16blend_arm:
push {r4-r10, lr} // stack ARM regs
mov r5, r1, lsr #24 // shift down alpha
mov r9, #0xff // create mask
add r5, r5, r5, lsr #7 // add in top bit
rsb r5, r5, #256 // invert alpha
and r10, r1, #0xff // extract red
and r12, r9, r1, lsr #8 // extract green
and r4, r9, r1, lsr #16 // extract blue
mov r10, r10, lsl #5 // prescale red
mov r12, r12, lsl #6 // prescale green
mov r4, r4, lsl #5 // prescale blue
mov r9, r9, lsr #2 // create dest green mask
1:
ldrh r8, [r0] // load dest pixel
subs r2, r2, #1 // decrement loop counter
mov r6, r8, lsr #11 // extract dest red
and r7, r9, r8, lsr #5 // extract dest green
and r8, r8, #0x1f // extract dest blue
smlabb r6, r6, r5, r10 // dest red * alpha + src red
smlabb r7, r7, r5, r12 // dest green * alpha + src green
smlabb r8, r8, r5, r4 // dest blue * alpha + src blue
mov r6, r6, lsr #8 // shift down red
mov r7, r7, lsr #8 // shift down green
mov r6, r6, lsl #11 // shift red into 565
orr r6, r7, lsl #5 // shift green into 565
orr r6, r8, lsr #8 // shift blue into 565
strh r6, [r0], #2 // store pixel to dest, update ptr
bne 1b // if count != 0, loop
pop {r4-r10, pc} // return
