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fixed artifact pattern left in TrueColor dithering code (visible with

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tiled gradients as wallpaper)
This commit is contained in:
kojima
2001-09-10 17:23:14 +00:00
parent 680b9d7731
commit e848fb0d74
1 changed files with 51 additions and 1 deletions
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52
wrlib/convert.c
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@@ -155,7 +155,6 @@ convertTrueColor_generic(RXImage *ximg, RImage *image,
unsigned char *ptr = image->data;
int channels = (image->format == RRGBAFormat ? 4 : 3);
/* convert and dither the image to XImage */
for (y=0; y<image->height; y++) {
nerr[0] = 0;
@@ -210,6 +209,57 @@ convertTrueColor_generic(RXImage *ximg, RImage *image,
err = nerr;
nerr = terr;
}
/* redither the 1st line to distribute error better */
ptr=image->data;
y=0;
nerr[0] = 0;
nerr[1] = 0;
nerr[2] = 0;
for (x=0; x<image->width; x++, ptr+=channels) {
/* reduce pixel */
pixel = *ptr + err[x];
if (pixel<0) pixel=0; else if (pixel>0xff) pixel=0xff;
r = rtable[pixel];
/* calc error */
rer = pixel - r*dr;
/* reduce pixel */
pixel = *(ptr+1) + err[x+1];
if (pixel<0) pixel=0; else if (pixel>0xff) pixel=0xff;
g = gtable[pixel];
/* calc error */
ger = pixel - g*dg;
/* reduce pixel */
pixel = *(ptr+2) + err[x+2];
if (pixel<0) pixel=0; else if (pixel>0xff) pixel=0xff;
b = btable[pixel];
/* calc error */
ber = pixel - b*db;
pixel = (r<<roffs) | (g<<goffs) | (b<<boffs);
XPutPixel(ximg->image, x, y, pixel);
/* distribute error */
r = (rer*3)/8;
g = (ger*3)/8;
b = (ber*3)/8;
/* x+1, y */
err[x+3*1]+=r;
err[x+1+3*1]+=g;
err[x+2+3*1]+=b;
/* x, y+1 */
nerr[x]+=r;
nerr[x+1]+=g;
nerr[x+2]+=b;
/* x+1, y+1 */
nerr[x+3*1]=rer-2*r;
nerr[x+1+3*1]=ger-2*g;
nerr[x+2+3*1]=ber-2*b;
}
}