Attachment 2859 Details for Bug 4096 – Patch

[patch] Patch

premultiply-patch.diff (text/plain), 1.56 KB, created by Billy Biggs on 2005-08-14 19:29:49 UTC

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Creator: Billy Biggs

Created: 2005-08-14 19:29:49 UTC

Size: 1.56 KB

patch

obsolete

>Index: cairo-png.c
>===================================================================
>RCS file: /cvs/cairo/cairo/src/cairo-png.c,v
>retrieving revision 1.21
>diff -p -u -r1.21 cairo-png.c
>--- cairo-png.c	28 Jul 2005 18:42:33 -0000	1.21
>+++ cairo-png.c	15 Aug 2005 02:26:20 -0000
>@@ -288,6 +288,13 @@ cairo_surface_write_to_png_stream (cairo
>     return write_png (surface, stream_write_func, &png_closure);
> }				     
> 
>+static __inline__ int
>+multiply_alpha (int a, int r)
>+{
>+    int temp = (r * a) + 0x80;
>+    return ((temp + (temp >> 8)) >> 8);
>+}
>+
> /* Premultiplies data and converts RGBA bytes => native endian */
> static void
> premultiply_data (png_structp   png,
>@@ -298,16 +305,23 @@ premultiply_data (png_structp   png,
> 
>     for (i = 0; i < row_info->rowbytes; i += 4) {
> 	uint8_t *base = &data[i];
>-	uint8_t  red = base[0];
>-	uint8_t  green = base[1];
>-	uint8_t  blue = base[2];
> 	uint8_t  alpha = base[3];
> 	uint32_t p;
> 
>-	red = ((unsigned) red * (unsigned) alpha + 127) / 255;
>-	green = ((unsigned) green * (unsigned) alpha + 127) / 255;
>-	blue = ((unsigned) blue * (unsigned) alpha + 127) / 255;
>-	p = (alpha << 24) | (red << 16) | (green << 8) | (blue << 0);
>+	if (alpha == 0) {
>+	    p = 0;
>+	} else {
>+	    uint8_t  red = base[0];
>+	    uint8_t  green = base[1];
>+	    uint8_t  blue = base[2];
>+
>+	    if (alpha != 0xff) {
>+		red = multiply_alpha (alpha, red);
>+		green = multiply_alpha (alpha, green);
>+		blue = multiply_alpha (alpha, blue);
>+	    }
>+	    p = (alpha << 24) | (red << 16) | (green << 8) | (blue << 0);
>+	}
> 	memcpy (base, &p, sizeof (uint32_t));
>     }
> }

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Attachments on bug 4096: 2859

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