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- /*
- * libpipi Pathetic image processing interface library
- * Copyright (c) 2004-2008 Sam Hocevar <sam@zoy.org>
- * All Rights Reserved
- *
- * $Id$
- *
- * This library is free software. It comes without any warranty, to
- * the extent permitted by applicable law. You can redistribute it
- * and/or modify it under the terms of the Do What The Fuck You Want
- * To Public License, Version 2, as published by Sam Hocevar. See
- * http://sam.zoy.org/wtfpl/COPYING for more details.
- */
-
- /*
- * ed.c: generic error diffusion functions
- */
-
- #include "config.h"
-
- #include "pipi.h"
- #include "pipi_internals.h"
-
- /* Perform a generic error diffusion dithering. The first non-zero
- * element in ker is treated as the current pixel. All other non-zero
- * elements are the error diffusion coefficients.
- * Making the matrix generic is not terribly slower: the performance
- * hit is around 4% for Floyd-Steinberg and 13% for JaJuNi, with the
- * benefit of a lot less code. */
- pipi_image_t *pipi_dither_ediff(pipi_image_t *img, pipi_image_t *ker,
- pipi_scan_t scan)
- {
- pipi_image_t *dst;
- pipi_pixels_t *dstp, *kerp;
- float *dstdata, *kerdata;
- int x, y, w, h, i, j, kx, kw, kh;
-
- w = img->w;
- h = img->h;
- kw = ker->w;
- kh = ker->h;
-
- dst = pipi_copy(img);
- dstp = pipi_getpixels(dst, PIPI_PIXELS_Y_F);
- dstdata = (float *)dstp->pixels;
-
- kerp = pipi_getpixels(ker, PIPI_PIXELS_Y_F);
- kerdata = (float *)kerp->pixels;
- for(kx = 0; kx < kw; kx++)
- if(kerdata[kx] > 0)
- break;
-
- for(y = 0; y < h; y++)
- {
- int reverse = (y & 1) && (scan == PIPI_SCAN_SERPENTINE);
-
- for(x = 0; x < w; x++)
- {
- float p, q, e;
- int x2 = reverse ? w - 1 - x : x;
- int s = reverse ? -1 : 1;
-
- p = dstdata[y * w + x2];
- q = p < 0.5 ? 0. : 1.;
- dstdata[y * w + x2] = q;
-
- e = (p - q);
-
- for(j = 0; j < kh && y < h - j; j++)
- for(i = 0; i < kw; i++)
- {
- if(j == 0 && i <= kx)
- continue;
-
- if(x + i - kx < 0 || x + i - kx >= w)
- continue;
-
- dstdata[(y + j) * w + x2 + (i - kx) * s]
- += e * kerdata[j * kw + i];
- }
- }
- }
-
- return dst;
- }
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