Changeset b22b449d in mainline

Timestamp:

2017-02-26T20:02:29Z (7 years ago)

Author:

Jiri Svoboda <jiri@…>

Branches:

lfn, master, serial, ticket/834-toolchain-update, topic/msim-upgrade, topic/simplify-dev-export

Children:

5b46ec8

Parents:

443a0bc

Message:

Alpha compositing does not need floating point.

File:

• uspace/lib/softrend/compose.c (modified) (1 diff)

uspace/lib/softrend/compose.c

@@ -53 +53 @@
 pixel_t compose_over(pixel_t fg, pixel_t bg)
 {
-        double mul;
-        double mul_cmp;
+        uint16_t mf;
+        uint16_t mb;
 
-        double res_a;
-        double res_r;
-        double res_g;
-        double res_b;
+        uint8_t res_a;
+        uint8_t res_r;
+        uint8_t res_g;
+        uint8_t res_b;
 
-        if (ALPHA(bg) == 255) {
-                res_a = 1;
-                mul = ((double) ALPHA(fg)) / 255.0;
-                mul_cmp = 1 - mul;
-        } else {
-                double fg_a = ((double) ALPHA(fg)) / 255.0;
-                double bg_a = ((double) ALPHA(bg)) / 255.0;
+        res_a = (ALPHA(fg) * 255 + (255 - ALPHA(fg)) * ALPHA(bg)) / 255;
+        mf = ALPHA(fg);
+        mb = (255 * 255 - ALPHA(fg) * ALPHA(bg)) / 255;
 
-                res_a = 1 - (1 - fg_a) * (1 - bg_a);
-                mul = fg_a / res_a;
-                mul_cmp = 1 - mul;
-        }
+        res_r = (mf * RED(fg) + mb * RED(bg)) / 255;
+        res_g = (mf * GREEN(fg) + mb * GREEN(bg)) / 255;
+        res_b = (mf * BLUE(fg) + mb * BLUE(bg)) / 255;
 
-        res_r = mul * ((double) RED(fg)) + mul_cmp * ((double) RED(bg));
-        res_g = mul * ((double) GREEN(fg)) + mul_cmp * ((double) GREEN(bg));
-        res_b = mul * ((double) BLUE(fg)) + mul_cmp * ((double) BLUE(bg));
-
-        return PIXEL((unsigned) (res_a * 255),
-            (unsigned) res_r, (unsigned) res_g, (unsigned) res_b);
+        return PIXEL(res_a, res_r, res_g, res_b);
 }