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Use minimal scale for jpeg drafts #2240

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merged 2 commits into from
Nov 22, 2016
Merged

Use minimal scale for jpeg drafts #2240

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8f6b7b2
use minimal scale for jpeg downscaling
homm Nov 22, 2016
55fca48
protect .draft() from second call
homm Nov 22, 2016
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6 changes: 5 additions & 1 deletion PIL/JpegImagePlugin.py
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Original file line number Diff line number Diff line change
Expand Up @@ -341,6 +341,10 @@ def draft(self, mode, size):
if len(self.tile) != 1:
return

# Protect from second call
if self.decoderconfig:
return

d, e, o, a = self.tile[0]
scale = 0

Expand All @@ -349,7 +353,7 @@ def draft(self, mode, size):
a = mode, ""

if size:
scale = max(self.size[0] // size[0], self.size[1] // size[1])
scale = min(self.size[0] // size[0], self.size[1] // size[1])
for s in [8, 4, 2, 1]:
if scale >= s:
break
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79 changes: 58 additions & 21 deletions Tests/test_image_draft.py
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Original file line number Diff line number Diff line change
Expand Up @@ -2,36 +2,73 @@

from PIL import Image

CODECS = dir(Image.core)
FILENAME = "Tests/images/hopper.jpg"
DATA = tostring(Image.open(FILENAME).resize((512, 512)), "JPEG")


def draft(mode, size):
im = fromstring(DATA)
im.draft(mode, size)
return im


class TestImageDraft(PillowTestCase):

def setUp(self):
if "jpeg_encoder" not in CODECS or "jpeg_decoder" not in CODECS:
codecs = dir(Image.core)
if "jpeg_encoder" not in codecs or "jpeg_decoder" not in codecs:
self.skipTest("jpeg support not available")

def draft_roundtrip(self, in_mode, in_size, req_mode, req_size):
im = Image.new(in_mode, in_size)
data = tostring(im, 'JPEG')
im = fromstring(data)
im.draft(req_mode, req_size)
return im

def test_size(self):
self.assertEqual(draft("RGB", (512, 512)).size, (512, 512))
self.assertEqual(draft("RGB", (256, 256)).size, (256, 256))
self.assertEqual(draft("RGB", (128, 128)).size, (128, 128))
self.assertEqual(draft("RGB", (64, 64)).size, (64, 64))
self.assertEqual(draft("RGB", (32, 32)).size, (64, 64))
for in_size, req_size, out_size in [
((435, 361), (2048, 2048), (435, 361)), # bigger
((435, 361), (435, 361), (435, 361)), # same
((128, 128), (64, 64), (64, 64)),
((128, 128), (32, 32), (32, 32)),
((128, 128), (16, 16), (16, 16)),

# large requested width
((435, 361), (218, 128), (435, 361)), # almost 2x
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Does this mean that if we request a draft image of (218, 128), we're getting something larger than that?

((435, 361), (217, 128), (218, 181)), # more than 2x
((435, 361), (109, 64), (218, 181)), # almost 4x
((435, 361), (108, 64), (109, 91)), # more than 4x
((435, 361), (55, 32), (109, 91)), # almost 8x
((435, 361), (54, 32), (55, 46)), # more than 8x
((435, 361), (27, 16), (55, 46)), # more than 16x

# and vice versa
((435, 361), (128, 181), (435, 361)), # almost 2x
((435, 361), (128, 180), (218, 181)), # more than 2x
((435, 361), (64, 91), (218, 181)), # almost 4x
((435, 361), (64, 90), (109, 91)), # more than 4x
((435, 361), (32, 46), (109, 91)), # almost 8x
((435, 361), (32, 45), (55, 46)), # more than 8x
((435, 361), (16, 22), (55, 46)), # more than 16x
]:
im = self.draft_roundtrip('L', in_size, None, req_size)
im.load()
self.assertEqual(im.size, out_size)

def test_mode(self):
self.assertEqual(draft("1", (512, 512)).mode, "RGB")
self.assertEqual(draft("L", (512, 512)).mode, "L")
self.assertEqual(draft("RGB", (512, 512)).mode, "RGB")
self.assertEqual(draft("YCbCr", (512, 512)).mode, "YCbCr")
for in_mode, req_mode, out_mode in [
("RGB", "1", "RGB"),
("RGB", "L", "L"),
("RGB", "RGB", "RGB"),
("RGB", "YCbCr", "YCbCr"),
("L", "1", "L"),
("L", "L", "L"),
("L", "RGB", "L"),
("L", "YCbCr", "L"),
("CMYK", "1", "CMYK"),
("CMYK", "L", "CMYK"),
("CMYK", "RGB", "CMYK"),
("CMYK", "YCbCr", "CMYK"),
]:
im = self.draft_roundtrip(in_mode, (64, 64), req_mode, None)
im.load()
self.assertEqual(im.mode, out_mode)

def test_several_drafts(self):
im = self.draft_roundtrip('L', (128, 128), None, (64, 64))
im.draft(None, (64, 64))
im.load()

if __name__ == '__main__':
unittest.main()