From 988fbb88dc621d8f41d1b07a729ae5afc24efdaa Mon Sep 17 00:00:00 2001 From: Ton Roosendaal Date: Wed, 29 Apr 2009 11:20:07 +0000 Subject: bugfix #18609 This fixes a commit from Peter, revision 12931, Dec 17 2007 He added quick image scaling code, derived from ppmqscale, http://libdv.sf.net This implementation gave ugly banding. especially visible on dark colors or byte images with very close colors. Solution is to add correct rounding, seems to me normal for such fixed point magic. Optimizing code and keeping quality is tricky dudes! Results for scaling down in sequencer were bad for over a year (2.47 and 2.48 both wrong). --- source/blender/imbuf/intern/scaling.c | 33 +++++++++++++++++---------------- 1 file changed, 17 insertions(+), 16 deletions(-) (limited to 'source/blender/imbuf') diff --git a/source/blender/imbuf/intern/scaling.c b/source/blender/imbuf/intern/scaling.c index 807b0c84e90..b308915cd62 100644 --- a/source/blender/imbuf/intern/scaling.c +++ b/source/blender/imbuf/intern/scaling.c @@ -609,34 +609,35 @@ static void shrink_picture_byte( w = (weight1y * weight1x) >> 16; - dst_line1[x].r += (line[0] * w) >> 16; - dst_line1[x].g += (line[1] * w) >> 16; - dst_line1[x].b += (line[2] * w) >> 16; - dst_line1[x].a += (line[3] * w) >> 16; + /* ensure correct rounding, without this you get ugly banding (ton) */ + dst_line1[x].r += (line[0] * w + 32767) >> 16; + dst_line1[x].g += (line[1] * w + 32767) >> 16; + dst_line1[x].b += (line[2] * w + 32767) >> 16; + dst_line1[x].a += (line[3] * w + 32767) >> 16; dst_line1[x].weight += w; w = (weight2y * weight1x) >> 16; - dst_line2[x].r += (line[0] * w) >> 16; - dst_line2[x].g += (line[1] * w) >> 16; - dst_line2[x].b += (line[2] * w) >> 16; - dst_line2[x].a += (line[3] * w) >> 16; + dst_line2[x].r += (line[0] * w + 32767) >> 16; + dst_line2[x].g += (line[1] * w + 32767) >> 16; + dst_line2[x].b += (line[2] * w + 32767) >> 16; + dst_line2[x].a += (line[3] * w + 32767) >> 16; dst_line2[x].weight += w; w = (weight1y * weight2x) >> 16; - dst_line1[x+1].r += (line[0] * w) >> 16; - dst_line1[x+1].g += (line[1] * w) >> 16; - dst_line1[x+1].b += (line[2] * w) >> 16; - dst_line1[x+1].a += (line[3] * w) >> 16; + dst_line1[x+1].r += (line[0] * w + 32767) >> 16; + dst_line1[x+1].g += (line[1] * w + 32767) >> 16; + dst_line1[x+1].b += (line[2] * w + 32767) >> 16; + dst_line1[x+1].a += (line[3] * w + 32767) >> 16; dst_line1[x+1].weight += w; w = (weight2y * weight2x) >> 16; - dst_line2[x+1].r += (line[0] * w) >> 16; - dst_line2[x+1].g += (line[1] * w) >> 16; - dst_line2[x+1].b += (line[2] * w) >> 16; - dst_line2[x+1].a += (line[3] * w) >> 16; + dst_line2[x+1].r += (line[0] * w + 32767) >> 16; + dst_line2[x+1].g += (line[1] * w + 32767) >> 16; + dst_line2[x+1].b += (line[2] * w + 32767) >> 16; + dst_line2[x+1].a += (line[3] * w + 32767) >> 16; dst_line2[x+1].weight += w; x_dst += dx_dst; -- cgit v1.2.3