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revise XYZ2CMYK fallback path

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better epsilon detect, add a test
This commit is contained in:
John Cupitt 2019-01-16 21:02:01 +00:00
parent a67f92b8d9
commit a7122d7a85
2 changed files with 25 additions and 20 deletions
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36
libvips/colour/XYZ2CMYK.c
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@ -150,26 +150,24 @@ vips_XYZ2CMYK_line( VipsColour *colour, VipsPel *out, VipsPel **in, int width )
float g = p[1] / VIPS_D65_Y0;
float b = p[2] / VIPS_D65_Z0;
float c, m, y, k;
float c = 1.0 - r;
float m = 1.0 - g;
float y = 1.0 - b;
float k = VIPS_MIN( c, VIPS_MIN( m, y ) );
float ik = 1.0 - k;
c = 255.0 - r;
m = 255.0 - g;
y = 255.0 - b;
k = VIPS_MIN( c, VIPS_MIN( m, y ) );
c = (c - k) / (255.0 - k) * 255.0;
m = (m - k) / (255.0 - k) * 255.0;
y = (y - k) / (255.0 - k) * 255.0;
q[0] = (unsigned char) VIPS_CLIP(0, c, 255.0);
q[1] = (unsigned char) VIPS_CLIP(0, m, 255.0);
q[2] = (unsigned char) VIPS_CLIP(0, y, 255.0);
if( r < epsilon &&
g < epsilon &&
b < epsilon )
q[3] = 255.0;
else
q[3] = VIPS_CLIP( 0, k, 255 );
if( ik < epsilon ) {
q[0] = 255;
q[1] = 255;
q[2] = 255;
q[3] = 255;
}
else {
q[0] = VIPS_CLIP( 0, 255 * (c - k) / ik, 255 );
q[1] = VIPS_CLIP( 0, 255 * (m - k) / ik, 255 );
q[2] = VIPS_CLIP( 0, 255 * (y - k) / ik, 255 );
q[3] = VIPS_CLIP( 0, 255 * k, 255 );
}
p += 3;
q += 4;

9
test/test-suite/test_colour.py
View File

@ -3,7 +3,7 @@ import pytest
import pyvips
from helpers import JPEG_FILE, SRGB_FILE, colour_colourspaces, \
mono_colourspaces, assert_almost_equal_objects
mono_colourspaces, assert_almost_equal_objects, skip_if_no
class TestColour:
@ -124,6 +124,7 @@ class TestColour:
assert abs(result - 4.97) < 0.5
assert pytest.approx(alpha, 0.001) == 42.0
@skip_if_no("icc_import")
def test_icc(self):
test = pyvips.Image.new_from_file(JPEG_FILE)
@ -163,6 +164,12 @@ class TestColour:
im = test.icc_import()
assert im.interpretation == pyvips.Interpretation.LAB
# even without lcms, we should have a working approximation
def test_cmyk(self):
test = pyvips.Image.new_from_file(JPEG_FILE)
im = test.colourspace("cmyk").colourspace("srgb")
if __name__ == '__main__':
pytest.main()