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80 lines
2.3 KiB
C
80 lines
2.3 KiB
C
/*
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* The Python Imaging Library
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* $Id$
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*
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* interpolate between two existing images
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*
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* history:
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* 96-03-20 fl Created
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* 96-05-18 fl Simplified blend expression
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* 96-10-05 fl Fixed expression bug, special case for interpolation
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*
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* Copyright (c) Fredrik Lundh 1996.
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* Copyright (c) Secret Labs AB 1997.
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*
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* See the README file for details on usage and redistribution.
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*/
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#include "Imaging.h"
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Imaging
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ImagingBlend(Imaging imIn1, Imaging imIn2, float alpha) {
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Imaging imOut;
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int x, y;
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/* Check arguments */
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if (!imIn1 || !imIn2 || imIn1->type != IMAGING_TYPE_UINT8 || imIn1->palette ||
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strcmp(imIn1->mode, "1") == 0 || imIn2->palette ||
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strcmp(imIn2->mode, "1") == 0) {
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return ImagingError_ModeError();
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}
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if (imIn1->type != imIn2->type || imIn1->bands != imIn2->bands ||
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imIn1->xsize != imIn2->xsize || imIn1->ysize != imIn2->ysize) {
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return ImagingError_Mismatch();
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}
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/* Shortcuts */
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if (alpha == 0.0) {
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return ImagingCopy(imIn1);
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} else if (alpha == 1.0) {
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return ImagingCopy(imIn2);
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}
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imOut = ImagingNewDirty(imIn1->mode, imIn1->xsize, imIn1->ysize);
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if (!imOut) {
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return NULL;
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}
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if (alpha >= 0 && alpha <= 1.0) {
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/* Interpolate between bands */
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for (y = 0; y < imIn1->ysize; y++) {
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UINT8 *in1 = (UINT8 *)imIn1->image[y];
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UINT8 *in2 = (UINT8 *)imIn2->image[y];
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UINT8 *out = (UINT8 *)imOut->image[y];
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for (x = 0; x < imIn1->linesize; x++) {
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out[x] = (UINT8)((int)in1[x] + alpha * ((int)in2[x] - (int)in1[x]));
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}
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}
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} else {
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/* Extrapolation; must make sure to clip resulting values */
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for (y = 0; y < imIn1->ysize; y++) {
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UINT8 *in1 = (UINT8 *)imIn1->image[y];
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UINT8 *in2 = (UINT8 *)imIn2->image[y];
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UINT8 *out = (UINT8 *)imOut->image[y];
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for (x = 0; x < imIn1->linesize; x++) {
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float temp = (float)((int)in1[x] + alpha * ((int)in2[x] - (int)in1[x]));
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if (temp <= 0.0) {
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out[x] = 0;
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} else if (temp >= 255.0) {
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out[x] = 255;
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} else {
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out[x] = (UINT8)temp;
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}
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}
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}
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}
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return imOut;
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}
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