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/*
* The Python Imaging Library
* $Id: Antialias.c 2408 2005-05-15 09:31:27Z Fredrik $
*
* pilopen antialiasing support
*
* history:
* 2002-03-09 fl Created (for PIL 1.1.3)
* 2002-03-10 fl Added support for mode "F"
*
* Copyright (c) 1997-2002 by Secret Labs AB
*
* See the README file for information on usage and redistribution.
*/
#include "Imaging.h"
#include <math.h>
/* resampling filters (from antialias.py) */
struct filter {
float (*filter)(float x);
float support;
};
static inline float sinc_filter(float x)
{
if (x == 0.0)
return 1.0;
x = x * M_PI;
return sin(x) / x;
}
static inline float antialias_filter(float x)
{
/* lanczos (truncated sinc) */
if (-3.0 <= x && x < 3.0)
return sinc_filter(x) * sinc_filter(x/3);
return 0.0;
}
static struct filter ANTIALIAS = { antialias_filter, 3.0 };
static inline float nearest_filter(float x)
{
if (-0.5 <= x && x < 0.5)
return 1.0;
return 0.0;
}
static struct filter NEAREST = { nearest_filter, 0.5 };
static inline float bilinear_filter(float x)
{
if (x < 0.0)
x = -x;
if (x < 1.0)
return 1.0-x;
return 0.0;
}
static struct filter BILINEAR = { bilinear_filter, 1.0 };
static inline float bicubic_filter(float x)
{
/* FIXME: double-check this algorithm */
/* FIXME: for best results, "a" should be -0.5 to -1.0, but we'll
set it to zero for now, to match the 1.1 magnifying filter */
#define a 0.0
if (x < 0.0)
x = -x;
if (x < 1.0)
return (((a + 2.0) * x) - (a + 3.0)) * x*x + 1;
if (x < 2.0)
return (((a * x) - 5*a) * x + 8) * x - 4*a;
return 0.0;
#undef a
}
static struct filter BICUBIC = { bicubic_filter, 2.0 };
Imaging
ImagingStretch(Imaging imOut, Imaging imIn, int filter)
{
/* FIXME: this is a quick and straightforward translation from a
python prototype. might need some further C-ification... */
ImagingSectionCookie cookie;
struct filter *filterp;
float support, scale, filterscale;
float center, ww, ss, ymin, ymax, xmin, xmax;
int xx, yy, x, y, b;
float *k;
/* check modes */
if (!imOut || !imIn || strcmp(imIn->mode, imOut->mode) != 0)
return (Imaging) ImagingError_ModeError();
/* check filter */
switch (filter) {
case IMAGING_TRANSFORM_NEAREST:
filterp = &NEAREST;
break;
case IMAGING_TRANSFORM_ANTIALIAS:
filterp = &ANTIALIAS;
break;
case IMAGING_TRANSFORM_BILINEAR:
filterp = &BILINEAR;
break;
case IMAGING_TRANSFORM_BICUBIC:
filterp = &BICUBIC;
break;
default:
return (Imaging) ImagingError_ValueError(
"unsupported resampling filter"
);
}
if (imIn->ysize == imOut->ysize) {
/* prepare for horizontal stretch */
filterscale = scale = (float) imIn->xsize / imOut->xsize;
} else if (imIn->xsize == imOut->xsize) {
/* prepare for vertical stretch */
filterscale = scale = (float) imIn->ysize / imOut->ysize;
} else
return (Imaging) ImagingError_Mismatch();
/* determine support size (length of resampling filter) */
support = filterp->support;
if (filterscale < 1.0) {
filterscale = 1.0;
support = 0.5;
}
support = support * filterscale;
/* coefficient buffer (with rounding safety margin) */
k = malloc(((int) support * 2 + 10) * sizeof(float));
if (!k)
return (Imaging) ImagingError_MemoryError();
ImagingSectionEnter(&cookie);
if (imIn->xsize == imOut->xsize) {
/* vertical stretch */
for (yy = 0; yy < imOut->ysize; yy++) {
center = (yy + 0.5) * scale;
ww = 0.0;
ss = 1.0 / filterscale;
/* calculate filter weights */
ymin = floor(center - support);
if (ymin < 0.0)
ymin = 0.0;
ymax = ceil(center + support);
if (ymax > imIn->ysize)
ymax = imIn->ysize;
for (y = (int) ymin; y < (int) ymax; y++) {
float w = filterp->filter((y - center + 0.5) * ss) * ss;
k[y - (int) ymin] = w;
ww = ww + w;
}
if (ww == 0.0)
ww = 1.0;
else
ww = 1.0 / ww;
if (imIn->image8) {
/* 8-bit grayscale */
for (xx = 0; xx < imOut->xsize; xx++) {
ss = 0.0;
for (y = (int) ymin; y < (int) ymax; y++)
ss = ss + imIn->image8[y][xx] * k[y - (int) ymin];
ss = ss * ww + 0.5;
if (ss < 0.5)
imOut->image8[yy][xx] = 0;
else if (ss >= 255.0)
imOut->image8[yy][xx] = 255;
else
imOut->image8[yy][xx] = (UINT8) ss;
}
} else
switch(imIn->type) {
case IMAGING_TYPE_UINT8:
/* n-bit grayscale */
for (xx = 0; xx < imOut->xsize*4; xx++) {
/* FIXME: skip over unused pixels */
ss = 0.0;
for (y = (int) ymin; y < (int) ymax; y++)
ss = ss + (UINT8) imIn->image[y][xx] * k[y-(int) ymin];
ss = ss * ww + 0.5;
if (ss < 0.5)
imOut->image[yy][xx] = (UINT8) 0;
else if (ss >= 255.0)
imOut->image[yy][xx] = (UINT8) 255;
else
imOut->image[yy][xx] = (UINT8) ss;
}
break;
case IMAGING_TYPE_INT32:
/* 32-bit integer */
for (xx = 0; xx < imOut->xsize; xx++) {
ss = 0.0;
for (y = (int) ymin; y < (int) ymax; y++)
ss = ss + IMAGING_PIXEL_I(imIn, xx, y) * k[y - (int) ymin];
IMAGING_PIXEL_I(imOut, xx, yy) = ss * ww;
}
break;
case IMAGING_TYPE_FLOAT32:
/* 32-bit float */
for (xx = 0; xx < imOut->xsize; xx++) {
ss = 0.0;
for (y = (int) ymin; y < (int) ymax; y++)
ss = ss + IMAGING_PIXEL_F(imIn, xx, y) * k[y - (int) ymin];
IMAGING_PIXEL_F(imOut, xx, yy) = ss * ww;
}
break;
default:
ImagingSectionLeave(&cookie);
return (Imaging) ImagingError_ModeError();
}
}
} else {
/* horizontal stretch */
for (xx = 0; xx < imOut->xsize; xx++) {
center = (xx + 0.5) * scale;
ww = 0.0;
ss = 1.0 / filterscale;
xmin = floor(center - support);
if (xmin < 0.0)
xmin = 0.0;
xmax = ceil(center + support);
if (xmax > imIn->xsize)
xmax = imIn->xsize;
for (x = (int) xmin; x < (int) xmax; x++) {
float w = filterp->filter((x - center + 0.5) * ss) * ss;
k[x - (int) xmin] = w;
ww = ww + w;
}
if (ww == 0.0)
ww = 1.0;
else
ww = 1.0 / ww;
if (imIn->image8) {
/* 8-bit grayscale */
for (yy = 0; yy < imOut->ysize; yy++) {
ss = 0.0;
for (x = (int) xmin; x < (int) xmax; x++)
ss = ss + imIn->image8[yy][x] * k[x - (int) xmin];
ss = ss * ww + 0.5;
if (ss < 0.5)
imOut->image8[yy][xx] = (UINT8) 0;
else if (ss >= 255.0)
imOut->image8[yy][xx] = (UINT8) 255;
else
imOut->image8[yy][xx] = (UINT8) ss;
}
} else
switch(imIn->type) {
case IMAGING_TYPE_UINT8:
/* n-bit grayscale */
for (yy = 0; yy < imOut->ysize; yy++) {
for (b = 0; b < imIn->bands; b++) {
if (imIn->bands == 2 && b)
b = 3; /* hack to deal with LA images */
ss = 0.0;
for (x = (int) xmin; x < (int) xmax; x++)
ss = ss + (UINT8) imIn->image[yy][x*4+b] * k[x - (int) xmin];
ss = ss * ww + 0.5;
if (ss < 0.5)
imOut->image[yy][xx*4+b] = (UINT8) 0;
else if (ss >= 255.0)
imOut->image[yy][xx*4+b] = (UINT8) 255;
else
imOut->image[yy][xx*4+b] = (UINT8) ss;
}
}
break;
case IMAGING_TYPE_INT32:
/* 32-bit integer */
for (yy = 0; yy < imOut->ysize; yy++) {
ss = 0.0;
for (x = (int) xmin; x < (int) xmax; x++)
ss = ss + IMAGING_PIXEL_I(imIn, x, yy) * k[x - (int) xmin];
IMAGING_PIXEL_I(imOut, xx, yy) = ss * ww;
}
break;
case IMAGING_TYPE_FLOAT32:
/* 32-bit float */
for (yy = 0; yy < imOut->ysize; yy++) {
ss = 0.0;
for (x = (int) xmin; x < (int) xmax; x++)
ss = ss + IMAGING_PIXEL_F(imIn, x, yy) * k[x - (int) xmin];
IMAGING_PIXEL_F(imOut, xx, yy) = ss * ww;
}
break;
default:
ImagingSectionLeave(&cookie);
return (Imaging) ImagingError_ModeError();
}
}
}
ImagingSectionLeave(&cookie);
free(k);
return imOut;
}
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