From 687c9a871033de00657b6f64f429f921ad0dd10f Mon Sep 17 00:00:00 2001
From: Calixte Denizet <calixte.denizet@gmail.com>
Date: Sat, 9 Apr 2022 20:18:29 +0200
Subject: [PATCH] Improve performance of applyMaskImageData - write some uint32
instead of uint8 to avoid the check before clamping; - unroll the loop to
write data in the buffer - but keep a loop for the last element of a line: it
likely doesn't hurt that much since it's executed only for one time for
each line; - I tested on a macbook with an Apple chip, and on Firefox nightly
the new code is almost 3.5x faster than before (~1.8x with Chrome).
---
src/shared/image_utils.js | 42 +++++++++++++++++++++++++--------------
1 file changed, 27 insertions(+), 15 deletions(-)
diff --git a/src/shared/image_utils.js b/src/shared/image_utils.js
index 69d843467..ecc07bc36 100644
--- a/src/shared/image_utils.js
+++ b/src/shared/image_utils.js
@@ -13,30 +13,42 @@
* limitations under the License.
*/
+import { FeatureTest } from "./util.js";
+
function applyMaskImageData({
src,
srcPos = 0,
dest,
- destPos = 3,
+ destPos = 0,
width,
height,
inverseDecode = false,
}) {
- const srcLength = src.byteLength;
- const zeroMapping = inverseDecode ? 0 : 255;
- const oneMapping = inverseDecode ? 255 : 0;
+ const opaque = FeatureTest.isLittleEndian ? 0xff000000 : 0x000000ff;
+ const [zeroMapping, oneMapping] = !inverseDecode ? [opaque, 0] : [0, opaque];
+ const widthInSource = width >> 3;
+ const widthRemainder = width & 7;
+ const srcLength = src.length;
+ dest = new Uint32Array(dest.buffer);
- for (let j = 0; j < height; j++) {
- let elem,
- mask = 0;
- for (let k = 0; k < width; k++) {
- if (mask === 0) {
- elem = srcPos < srcLength ? src[srcPos++] : 255;
- mask = 128;
- }
- dest[destPos] = elem & mask ? oneMapping : zeroMapping;
- destPos += 4;
- mask >>= 1;
+ for (let i = 0; i < height; i++) {
+ for (const max = srcPos + widthInSource; srcPos < max; srcPos++) {
+ const elem = srcPos < srcLength ? src[srcPos] : 255;
+ dest[destPos++] = elem & 0b10000000 ? oneMapping : zeroMapping;
+ dest[destPos++] = elem & 0b1000000 ? oneMapping : zeroMapping;
+ dest[destPos++] = elem & 0b100000 ? oneMapping : zeroMapping;
+ dest[destPos++] = elem & 0b10000 ? oneMapping : zeroMapping;
+ dest[destPos++] = elem & 0b1000 ? oneMapping : zeroMapping;
+ dest[destPos++] = elem & 0b100 ? oneMapping : zeroMapping;
+ dest[destPos++] = elem & 0b10 ? oneMapping : zeroMapping;
+ dest[destPos++] = elem & 0b1 ? oneMapping : zeroMapping;
+ }
+ if (widthRemainder === 0) {
+ continue;
+ }
+ const elem = srcPos < srcLength ? src[srcPos++] : 255;
+ for (let j = 0; j < widthRemainder; j++) {
+ dest[destPos++] = elem & (1 << (7 - j)) ? oneMapping : zeroMapping;
}
}