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https://github.com/python-pillow/Pillow.git
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308 lines
10 KiB
C
308 lines
10 KiB
C
/*
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* The Python Imaging Library
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* $Id$
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*
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* pilopen antialiasing support
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*
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* history:
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* 2002-03-09 fl Created (for PIL 1.1.3)
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* 2002-03-10 fl Added support for mode "F"
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*
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* Copyright (c) 1997-2002 by Secret Labs AB
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*
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* See the README file for information on usage and redistribution.
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*/
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#include "Imaging.h"
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#include <math.h>
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/* resampling filters (from antialias.py) */
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struct filter {
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float (*filter)(float x);
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float support;
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};
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static inline float sinc_filter(float x)
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{
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if (x == 0.0)
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return 1.0;
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x = x * M_PI;
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return sin(x) / x;
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}
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static inline float antialias_filter(float x)
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{
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/* lanczos (truncated sinc) */
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if (-3.0 <= x && x < 3.0)
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return sinc_filter(x) * sinc_filter(x/3);
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return 0.0;
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}
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static struct filter ANTIALIAS = { antialias_filter, 3.0 };
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static inline float nearest_filter(float x)
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{
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if (-0.5 <= x && x < 0.5)
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return 1.0;
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return 0.0;
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}
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static struct filter NEAREST = { nearest_filter, 0.5 };
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static inline float bilinear_filter(float x)
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{
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if (x < 0.0)
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x = -x;
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if (x < 1.0)
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return 1.0-x;
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return 0.0;
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}
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static struct filter BILINEAR = { bilinear_filter, 1.0 };
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static inline float bicubic_filter(float x)
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{
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/* FIXME: double-check this algorithm */
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/* FIXME: for best results, "a" should be -0.5 to -1.0, but we'll
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set it to zero for now, to match the 1.1 magnifying filter */
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#define a 0.0
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if (x < 0.0)
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x = -x;
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if (x < 1.0)
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return (((a + 2.0) * x) - (a + 3.0)) * x*x + 1;
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if (x < 2.0)
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return (((a * x) - 5*a) * x + 8) * x - 4*a;
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return 0.0;
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#undef a
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}
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static struct filter BICUBIC = { bicubic_filter, 2.0 };
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Imaging
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ImagingStretch(Imaging imOut, Imaging imIn, int filter)
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{
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/* FIXME: this is a quick and straightforward translation from a
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python prototype. might need some further C-ification... */
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ImagingSectionCookie cookie;
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struct filter *filterp;
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float support, scale, filterscale;
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float center, ww, ss, ymin, ymax, xmin, xmax;
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int xx, yy, x, y, b;
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float *k;
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/* check modes */
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if (!imOut || !imIn || strcmp(imIn->mode, imOut->mode) != 0)
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return (Imaging) ImagingError_ModeError();
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/* check filter */
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switch (filter) {
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case IMAGING_TRANSFORM_NEAREST:
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filterp = &NEAREST;
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break;
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case IMAGING_TRANSFORM_ANTIALIAS:
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filterp = &ANTIALIAS;
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break;
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case IMAGING_TRANSFORM_BILINEAR:
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filterp = &BILINEAR;
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break;
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case IMAGING_TRANSFORM_BICUBIC:
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filterp = &BICUBIC;
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break;
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default:
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return (Imaging) ImagingError_ValueError(
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"unsupported resampling filter"
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);
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}
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if (imIn->ysize == imOut->ysize) {
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/* prepare for horizontal stretch */
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filterscale = scale = (float) imIn->xsize / imOut->xsize;
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} else if (imIn->xsize == imOut->xsize) {
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/* prepare for vertical stretch */
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filterscale = scale = (float) imIn->ysize / imOut->ysize;
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} else
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return (Imaging) ImagingError_Mismatch();
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/* determine support size (length of resampling filter) */
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support = filterp->support;
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if (filterscale < 1.0) {
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filterscale = 1.0;
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support = 0.5;
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}
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support = support * filterscale;
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/* coefficient buffer (with rounding safety margin) */
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k = malloc(((int) support * 2 + 10) * sizeof(float));
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if (!k)
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return (Imaging) ImagingError_MemoryError();
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ImagingSectionEnter(&cookie);
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if (imIn->xsize == imOut->xsize) {
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/* vertical stretch */
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for (yy = 0; yy < imOut->ysize; yy++) {
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center = (yy + 0.5) * scale;
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ww = 0.0;
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ss = 1.0 / filterscale;
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/* calculate filter weights */
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ymin = floor(center - support);
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if (ymin < 0.0)
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ymin = 0.0;
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ymax = ceil(center + support);
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if (ymax > (float) imIn->ysize)
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ymax = (float) imIn->ysize;
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for (y = (int) ymin; y < (int) ymax; y++) {
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float w = filterp->filter((y - center + 0.5) * ss) * ss;
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k[y - (int) ymin] = w;
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ww = ww + w;
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}
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if (ww == 0.0)
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ww = 1.0;
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else
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ww = 1.0 / ww;
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if (imIn->image8) {
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/* 8-bit grayscale */
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for (xx = 0; xx < imOut->xsize; xx++) {
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ss = 0.0;
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for (y = (int) ymin; y < (int) ymax; y++)
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ss = ss + imIn->image8[y][xx] * k[y - (int) ymin];
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ss = ss * ww + 0.5;
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if (ss < 0.5)
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imOut->image8[yy][xx] = 0;
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else if (ss >= 255.0)
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imOut->image8[yy][xx] = 255;
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else
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imOut->image8[yy][xx] = (UINT8) ss;
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}
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} else
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switch(imIn->type) {
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case IMAGING_TYPE_UINT8:
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/* n-bit grayscale */
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for (xx = 0; xx < imOut->xsize*4; xx++) {
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/* FIXME: skip over unused pixels */
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ss = 0.0;
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for (y = (int) ymin; y < (int) ymax; y++)
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ss = ss + (UINT8) imIn->image[y][xx] * k[y-(int) ymin];
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ss = ss * ww + 0.5;
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if (ss < 0.5)
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imOut->image[yy][xx] = (UINT8) 0;
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else if (ss >= 255.0)
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imOut->image[yy][xx] = (UINT8) 255;
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else
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imOut->image[yy][xx] = (UINT8) ss;
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}
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break;
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case IMAGING_TYPE_INT32:
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/* 32-bit integer */
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for (xx = 0; xx < imOut->xsize; xx++) {
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ss = 0.0;
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for (y = (int) ymin; y < (int) ymax; y++)
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ss = ss + IMAGING_PIXEL_I(imIn, xx, y) * k[y - (int) ymin];
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IMAGING_PIXEL_I(imOut, xx, yy) = (int) ss * ww;
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}
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break;
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case IMAGING_TYPE_FLOAT32:
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/* 32-bit float */
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for (xx = 0; xx < imOut->xsize; xx++) {
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ss = 0.0;
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for (y = (int) ymin; y < (int) ymax; y++)
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ss = ss + IMAGING_PIXEL_F(imIn, xx, y) * k[y - (int) ymin];
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IMAGING_PIXEL_F(imOut, xx, yy) = ss * ww;
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}
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break;
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default:
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ImagingSectionLeave(&cookie);
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return (Imaging) ImagingError_ModeError();
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}
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}
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} else {
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/* horizontal stretch */
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for (xx = 0; xx < imOut->xsize; xx++) {
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center = (xx + 0.5) * scale;
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ww = 0.0;
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ss = 1.0 / filterscale;
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xmin = floor(center - support);
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if (xmin < 0.0)
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xmin = 0.0;
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xmax = ceil(center + support);
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if (xmax > (float) imIn->xsize)
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xmax = (float) imIn->xsize;
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for (x = (int) xmin; x < (int) xmax; x++) {
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float w = filterp->filter((x - center + 0.5) * ss) * ss;
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k[x - (int) xmin] = w;
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ww = ww + w;
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}
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if (ww == 0.0)
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ww = 1.0;
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else
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ww = 1.0 / ww;
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if (imIn->image8) {
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/* 8-bit grayscale */
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for (yy = 0; yy < imOut->ysize; yy++) {
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ss = 0.0;
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for (x = (int) xmin; x < (int) xmax; x++)
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ss = ss + imIn->image8[yy][x] * k[x - (int) xmin];
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ss = ss * ww + 0.5;
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if (ss < 0.5)
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imOut->image8[yy][xx] = (UINT8) 0;
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else if (ss >= 255.0)
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imOut->image8[yy][xx] = (UINT8) 255;
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else
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imOut->image8[yy][xx] = (UINT8) ss;
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}
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} else
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switch(imIn->type) {
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case IMAGING_TYPE_UINT8:
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/* n-bit grayscale */
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for (yy = 0; yy < imOut->ysize; yy++) {
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for (b = 0; b < imIn->bands; b++) {
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if (imIn->bands == 2 && b)
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b = 3; /* hack to deal with LA images */
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ss = 0.0;
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for (x = (int) xmin; x < (int) xmax; x++)
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ss = ss + (UINT8) imIn->image[yy][x*4+b] * k[x - (int) xmin];
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ss = ss * ww + 0.5;
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if (ss < 0.5)
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imOut->image[yy][xx*4+b] = (UINT8) 0;
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else if (ss >= 255.0)
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imOut->image[yy][xx*4+b] = (UINT8) 255;
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else
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imOut->image[yy][xx*4+b] = (UINT8) ss;
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}
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}
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break;
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case IMAGING_TYPE_INT32:
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/* 32-bit integer */
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for (yy = 0; yy < imOut->ysize; yy++) {
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ss = 0.0;
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for (x = (int) xmin; x < (int) xmax; x++)
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ss = ss + IMAGING_PIXEL_I(imIn, x, yy) * k[x - (int) xmin];
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IMAGING_PIXEL_I(imOut, xx, yy) = (int) ss * ww;
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}
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break;
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case IMAGING_TYPE_FLOAT32:
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/* 32-bit float */
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for (yy = 0; yy < imOut->ysize; yy++) {
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ss = 0.0;
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for (x = (int) xmin; x < (int) xmax; x++)
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ss = ss + IMAGING_PIXEL_F(imIn, x, yy) * k[x - (int) xmin];
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IMAGING_PIXEL_F(imOut, xx, yy) = ss * ww;
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}
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break;
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default:
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ImagingSectionLeave(&cookie);
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return (Imaging) ImagingError_ModeError();
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}
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}
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}
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ImagingSectionLeave(&cookie);
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free(k);
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return imOut;
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}
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