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Simplify pdf image output. #15175

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Merged
merged 1 commit into from
Sep 12, 2019
Merged

Simplify pdf image output. #15175

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44 changes: 20 additions & 24 deletions lib/matplotlib/backends/backend_pdf.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1412,14 +1412,14 @@ def imageObject(self, image):

def _unpack(self, im):
"""
Unpack the image object im into height, width, data, alpha,
where data and alpha are HxWx3 (RGB) or HxWx1 (grayscale or alpha)
arrays, except alpha is None if the image is fully opaque.
Unpack image array *im* into ``(data, alpha)``, which have shape
``(height, width, 3)`` (RGB) or ``(height, width, 1)`` (grayscale or
alpha), except that alpha is None if the image is fully opaque.
"""
h, w = im.shape[:2]
im = im[::-1]
if im.ndim == 2:
return h, w, im, None
return im, None
else:
rgb = im[:, :, :3]
rgb = np.array(rgb, order='C')
Expand All @@ -1432,7 +1432,7 @@ def _unpack(self, im):
alpha = np.array(alpha, order='C')
else:
alpha = None
return h, w, rgb, alpha
return rgb, alpha

def _writePng(self, data):
"""
Expand All @@ -1455,27 +1455,24 @@ def _writePng(self, data):
buffer.seek(length, 1)
buffer.seek(4, 1) # skip CRC

def _writeImg(self, data, height, width, grayscale, id, smask=None):
def _writeImg(self, data, id, smask=None):
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do we ever actually pass in a grayscale image?

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We do pass single-channel images (for alpha). As for actual grayscale I don't know (see #12871 for the similar thing in postscript), but this PR doesn't change that behavior anyways.

"""
Write the image *data* of size *height* x *width*, as grayscale
if *grayscale* is true and RGB otherwise, as pdf object *id*
and with the soft mask (alpha channel) *smask*, which should be
either None or a *height* x *width* x 1 array.
Write the image *data*, of shape ``(height, width, 1)`` (grayscale) or
``(height, width, 3)`` (RGB), as pdf object *id* and with the soft mask
(alpha channel) *smask*, which should be either None or a ``(height,
width, 1)`` array.
"""

obj = {'Type': Name('XObject'),
'Subtype': Name('Image'),
'Width': width,
'Height': height,
'ColorSpace': Name('DeviceGray' if grayscale
else 'DeviceRGB'),
height, width, colors = data.shape
obj = {'Type': Name('XObject'),
'Subtype': Name('Image'),
'Width': width,
'Height': height,
'ColorSpace': Name({1: 'DeviceGray', 3: 'DeviceRGB'}[colors]),
'BitsPerComponent': 8}
if smask:
obj['SMask'] = smask
if rcParams['pdf.compression']:
png = {'Predictor': 10,
'Colors': 1 if grayscale else 3,
'Columns': width}
png = {'Predictor': 10, 'Colors': colors, 'Columns': width}
else:
png = None
self.beginStream(
Expand All @@ -1492,14 +1489,13 @@ def _writeImg(self, data, height, width, grayscale, id, smask=None):

def writeImages(self):
for img, name, ob in self._images.values():
height, width, data, adata = self._unpack(img)
data, adata = self._unpack(img)
if adata is not None:
smaskObject = self.reserveObject("smask")
self._writeImg(adata, height, width, True, smaskObject.id)
self._writeImg(adata, smaskObject.id)
else:
smaskObject = None
self._writeImg(data, height, width, False,
ob.id, smaskObject)
self._writeImg(data, ob.id, smaskObject)

def markerObject(self, path, trans, fill, stroke, lw, joinstyle,
capstyle):
Expand Down