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