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normalize coefficients in normalize_coeffs_8bpc

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increase precision of negative filter lobes. Add test
This commit is contained in:
homm 2016-07-03 02:09:39 +03:00 committed by wiredfool
parent 788810f313
commit 5c0eb2c365
2 changed files with 53 additions and 22 deletions
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17
Tests/test_image_resample.py
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@ -320,5 +320,22 @@ class CoreResamplePassesTest(PillowTestCase):
self.assertEqual(Image.core.getcount(), count + 2)
class CoreResampleCoefficientsTest(PillowTestCase):
def test_reduce(self):
test_color = 254
# print ''
for size in range(400000, 400010, 2):
# print '\r', size,
i = Image.new('L', (size, 1), 0)
draw = ImageDraw.Draw(i)
draw.rectangle((0, 0, i.size[0] // 2 - 1, 0), test_color)
px = i.resize((5, i.size[1]), Image.BICUBIC).load()
if px[2, 0] != test_color // 2:
self.assertEqual(test_color // 2, px[2, 0])
# print '\r>', size, test_color // 2, px[2, 0]
if __name__ == '__main__':
unittest.main()

54
libImaging/Resample.c
View File

@ -206,6 +206,32 @@ precompute_coeffs(int inSize, int outSize, struct filter *filterp,
}
int
normalize_coeffs_8bpc(int outSize, int kmax, double *prekk, INT32 **kkp)
{
int x;
INT32 *kk;
/* malloc check ok, overflow checked in precompute_coeffs */
kk = malloc(outSize * kmax * sizeof(INT32));
if ( ! kk) {
return 0;
}
for (x = 0; x < outSize * kmax; x++) {
if (prekk[x] < 0) {
kk[x] = (int) (-0.5 + prekk[x] * (1 << PRECISION_BITS));
} else {
kk[x] = (int) (0.5 + prekk[x] * (1 << PRECISION_BITS));
}
}
*kkp = kk;
return kmax;
}
Imaging
ImagingResampleHorizontal_8bpc(Imaging imIn, int xsize, struct filter *filterp)
{
@ -214,7 +240,7 @@ ImagingResampleHorizontal_8bpc(Imaging imIn, int xsize, struct filter *filterp)
int ss0, ss1, ss2, ss3;
int xx, yy, x, kmax, xmin, xmax;
int *xbounds;
int *k, *kk;
INT32 *k, *kk;
double *prekk;
kmax = precompute_coeffs(imIn->xsize, xsize, filterp, &xbounds, &prekk);
@ -222,19 +248,13 @@ ImagingResampleHorizontal_8bpc(Imaging imIn, int xsize, struct filter *filterp)
return (Imaging) ImagingError_MemoryError();
}
kk = malloc(xsize * kmax * sizeof(int));
if ( ! kk) {
kmax = normalize_coeffs_8bpc(xsize, kmax, prekk, &kk);
free(prekk);
if ( ! kmax) {
free(xbounds);
free(prekk);
return (Imaging) ImagingError_MemoryError();
}
for (x = 0; x < xsize * kmax; x++) {
kk[x] = (int) (0.5 + prekk[x] * (1 << PRECISION_BITS));
}
free(prekk);
imOut = ImagingNew(imIn->mode, xsize, imIn->ysize);
if ( ! imOut) {
free(kk);
@ -325,7 +345,7 @@ ImagingResampleVertical_8bpc(Imaging imIn, int ysize, struct filter *filterp)
int ss0, ss1, ss2, ss3;
int xx, yy, y, kmax, ymin, ymax;
int *xbounds;
int *k, *kk;
INT32 *k, *kk;
double *prekk;
kmax = precompute_coeffs(imIn->ysize, ysize, filterp, &xbounds, &prekk);
@ -333,19 +353,13 @@ ImagingResampleVertical_8bpc(Imaging imIn, int ysize, struct filter *filterp)
return (Imaging) ImagingError_MemoryError();
}
kk = malloc(ysize * kmax * sizeof(int));
if ( ! kk) {
kmax = normalize_coeffs_8bpc(ysize, kmax, prekk, &kk);
free(prekk);
if ( ! kmax) {
free(xbounds);
free(prekk);
return (Imaging) ImagingError_MemoryError();
}
for (y = 0; y < ysize * kmax; y++) {
kk[y] = (int) (0.5 + prekk[y] * (1 << PRECISION_BITS));
}
free(prekk);
imOut = ImagingNew(imIn->mode, imIn->xsize, ysize);
if ( ! imOut) {
free(kk);