| 1 | /* |
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| 2 | * edd error diffusion displacement |
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| 3 | * Copyright (c) 2008 Sam Hocevar <sam@zoy.org> |
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| 4 | * All Rights Reserved |
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| 5 | * |
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| 6 | * $Id$ |
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| 7 | * |
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| 8 | * This program is free software. It comes without any warranty, to |
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| 9 | * the extent permitted by applicable law. You can redistribute it |
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| 10 | * and/or modify it under the terms of the Do What The Fuck You Want |
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| 11 | * To Public License, Version 2, as published by Sam Hocevar. See |
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| 12 | * http://sam.zoy.org/wtfpl/COPYING for more details. |
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| 13 | */ |
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| 14 | |
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| 15 | /* This program computes the Floyd-Steinberg error diffusion algorithm's |
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| 16 | * displacement on the given input image. Error diffusion displacement is |
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| 17 | * introduced in the paper "Reinstating Floyd-Steinberg: Improved Metrics |
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| 18 | * for Quality Assessment of Error Diffusion Algorithms.", ICISP 2008 |
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| 19 | * Proceedings. Lecture Notes in Computer Science 5099 Springer 2008, ISBN |
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| 20 | * 978-3-540-69904-0. |
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| 21 | * |
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| 22 | * The resulting dx/dy values are usually around 0.16/0.26 for images that |
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| 23 | * are not entirely black and white. */ |
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| 24 | |
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| 25 | #include "config.h" |
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| 26 | #include "common.h" |
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| 27 | |
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| 28 | #include <stdio.h> |
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| 29 | #include <stdlib.h> |
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| 30 | #include <string.h> |
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| 31 | |
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| 32 | #include <pipi.h> |
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| 33 | |
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| 34 | #define Z 3 |
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| 35 | |
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| 36 | int main(int argc, char *argv[]) |
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| 37 | { |
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| 38 | double sigma = 1.2, precision = 0.001, step = 2.; |
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| 39 | double best = 1., fx = -1., fy = -1., bfx = 0., bfy = 0.; |
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| 40 | double e, e0, e1; |
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| 41 | pipi_image_t *img, *gauss, *dither, *tmp; |
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| 42 | int dx, dy; |
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| 43 | |
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| 44 | if(argc < 2) |
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| 45 | { |
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| 46 | fprintf(stderr, "%s: too few arguments\n", argv[0]); |
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| 47 | fprintf(stderr, "Usage: %s <image>\n", argv[0]); |
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| 48 | return EXIT_FAILURE; |
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| 49 | } |
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| 50 | |
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| 51 | /* Load image, convert it to grayscale, dither it with Floyd-Steinberg */ |
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| 52 | img = pipi_load(argv[1]); |
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| 53 | pipi_getpixels(img, PIPI_PIXELS_Y_F); |
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| 54 | gauss = pipi_gaussian_blur(img, sigma); |
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| 55 | dither = pipi_dither_floydsteinberg(img, PIPI_SCAN_RASTER); |
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| 56 | pipi_free(img); |
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| 57 | |
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| 58 | /* Compute the standard error */ |
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| 59 | tmp = pipi_gaussian_blur(dither, sigma); |
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| 60 | e0 = pipi_measure_msd(gauss, tmp); |
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| 61 | pipi_free(tmp); |
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| 62 | |
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| 63 | /* Compute the fast error */ |
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| 64 | tmp = pipi_gaussian_blur_ext(dither, sigma, sigma, 0.16, 0.26); |
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| 65 | e1 = pipi_measure_msd(gauss, tmp); |
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| 66 | pipi_free(tmp); |
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| 67 | |
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| 68 | /* Compute displacement */ |
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| 69 | while(step > precision) |
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| 70 | { |
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| 71 | for(dy = 0; dy <= Z; dy++) |
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| 72 | for(dx = 0; dx <= Z; dx++) |
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| 73 | { |
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| 74 | tmp = pipi_gaussian_blur_ext(dither, sigma, sigma, |
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| 75 | fx + step * dx / Z, |
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| 76 | fy + step * dy / Z); |
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| 77 | e = pipi_measure_msd(gauss, tmp); |
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| 78 | pipi_free(tmp); |
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| 79 | if(e < best) |
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| 80 | { |
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| 81 | best = e; |
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| 82 | bfx = fx + step * dx / Z; |
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| 83 | bfy = fy + step * dy / Z; |
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| 84 | } |
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| 85 | } |
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| 86 | |
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| 87 | fx = bfx - step / Z; |
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| 88 | fy = bfy - step / Z; |
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| 89 | step = step * 2 / Z; |
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| 90 | } |
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| 91 | |
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| 92 | printf("E: %g E_fast: %g E_min: %g dx: %g dy: %g\n", e0, e1, best, fx, fy); |
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| 93 | |
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| 94 | pipi_free(dither); |
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| 95 | pipi_free(gauss); |
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| 96 | |
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| 97 | return 0; |
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| 98 | } |
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| 99 | |
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