Hello,
i made a patch which would allow the svg backend to make
rasterized plots according to the dpi given in savefig.
I wanted this in order to have high-res scatter plots.
As you probably know it is hardcoded to 72 dpi right now.
The idea how to, came from the pdf backend. I mostly
copy pasted some code.
I also added a test for it. Some other tests now fail
the image comparison. It is nothing serious apparently.
Probably roundoff errors. Except interp_nearest_vs_none.
The result of which looks now exactly like the pdf which
it did not before.
Also, two other minor changes which i needed
- Compare_images failed for older numy versions. Simple fix ...
- A numpy.float32 variable got passed to the pdfRepr function in
backend_pdf.py. I changed this function to accept this type, too.
Cheers,
Michael
>From 309c93c2e71a7ef8d70deaf1f4d0c6adc77a0472 Mon Sep 17 00:00:00 2001
From: Michael Welter <mwel...@lusi.uni-sb.de>
Date: Sun, 26 Aug 2012 10:10:46 +0200
Subject: [PATCH 1/2] fixed: compare_images for older numpy versions. added:
backend_pdf allows numpy.float32 in pdfRepr
---
lib/matplotlib/backends/backend_pdf.py | 2 +-
lib/matplotlib/testing/compare.py | 4 ++--
2 files changed, 3 insertions(+), 3 deletions(-)
diff --git a/lib/matplotlib/backends/backend_pdf.py
b/lib/matplotlib/backends/backend_pdf.py
index 4cd8308..7acaddd 100644
--- a/lib/matplotlib/backends/backend_pdf.py
+++ b/lib/matplotlib/backends/backend_pdf.py
@@ -139,7 +139,7 @@ def pdfRepr(obj):
# Floats. PDF does not have exponential notation (1.0e-10) so we
# need to use %f with some precision. Perhaps the precision
# should adapt to the magnitude of the number?
- elif isinstance(obj, float):
+ elif isinstance(obj, (float, np.float32)):
if not np.isfinite(obj):
raise ValueError("Can only output finite numbers in PDF")
r = ("%.10f" % obj).encode('ascii')
diff --git a/lib/matplotlib/testing/compare.py
b/lib/matplotlib/testing/compare.py
index abd4f4f..8563147 100644
--- a/lib/matplotlib/testing/compare.py
+++ b/lib/matplotlib/testing/compare.py
@@ -308,8 +308,8 @@ def compare_images( expected, actual, tol,
in_decorator=False ):
h1p = expectedImage[:,:,i]
h2p = actualImage[:,:,i]
- h1h = np.histogram(h1p, bins=bins)[0]
- h2h = np.histogram(h2p, bins=bins)[0]
+ h1h = np.histogram(h1p, bins=ns)[0]
+ h2h = np.histogram(h2p, bins=ns)[0]
rms += np.sum(np.power((h1h-h2h), 2))
--
1.7.4.1
>From cb1aa376c8aa0e7d977174b53fd72b7fd6badfb5 Mon Sep 17 00:00:00 2001
From: Michael Welter <mwel...@lusi.uni-sb.de>
Date: Sun, 26 Aug 2012 17:18:08 +0200
Subject: [PATCH 2/2] fix: dpi setting should work now for rasterization in svg
backend
---
lib/matplotlib/backends/backend_svg.py | 33 ++++++++++++++++++++-----------
lib/matplotlib/tests/test_image.py | 27 ++++++++++++++++++++++++++
2 files changed, 48 insertions(+), 12 deletions(-)
diff --git a/lib/matplotlib/backends/backend_svg.py
b/lib/matplotlib/backends/backend_svg.py
index 0b9b7ab..f1c709c 100644
--- a/lib/matplotlib/backends/backend_svg.py
+++ b/lib/matplotlib/backends/backend_svg.py
@@ -244,10 +244,11 @@ class RendererSVG(RendererBase):
FONT_SCALE = 100.0
fontd = maxdict(50)
- def __init__(self, width, height, svgwriter, basename=None):
+ def __init__(self, width, height, image_dpi, svgwriter, basename=None):
self.width = width
self.height = height
self.writer = XMLWriter(svgwriter)
+ self.image_dpi = image_dpi # the actual dpi we want to rasterize stuff
with
self._groupd = {}
if not rcParams['svg.image_inline']:
@@ -733,6 +734,11 @@ class RendererSVG(RendererBase):
def option_scale_image(self):
return True
+
+ def get_image_magnification(self):
+ return self.image_dpi/72.0
+
+
def draw_image(self, gc, x, y, im, dx=None, dy=None, transform=None):
attrib = {}
clipid = self._get_clip(gc)
@@ -755,6 +761,17 @@ class RendererSVG(RendererBase):
im.resize(numcols, numrows)
h,w = im.get_size_out()
+
+ if dx is None:
+ w = 72.0*w/self.image_dpi
+ else:
+ w = dx
+
+ if dy is None:
+ h = 72.0*h/self.image_dpi
+ else:
+ h = dy
+
oid = getattr(im, '_gid', None)
url = getattr(im, '_url', None)
if url is not None:
@@ -1113,25 +1130,17 @@ class FigureCanvasSVG(FigureCanvasBase):
def _print_svg(self, filename, svgwriter, fh_to_close=None, **kwargs):
try:
+ image_dpi = kwargs.pop("dpi", 72)
self.figure.set_dpi(72.0)
width, height = self.figure.get_size_inches()
w, h = width*72, height*72
if rcParams['svg.image_noscale']:
- renderer = RendererSVG(w, h, svgwriter, filename)
+ renderer = RendererSVG(w, h, image_dpi, svgwriter, filename)
else:
- # setting mixed renderer dpi other than 72 results in
- # incorrect size of the rasterized image. It seems that the
- # svg internally uses fixed dpi of 72 and seems to cause
- # the problem. I hope someone who knows the svg backends
- # take a look at this problem. Meanwhile, the dpi
- # parameter is ignored and image_dpi is fixed at 72. - JJL
-
- #image_dpi = kwargs.pop("dpi", 72)
- image_dpi = 72
_bbox_inches_restore = kwargs.pop("bbox_inches_restore", None)
renderer = MixedModeRenderer(self.figure,
- width, height, image_dpi, RendererSVG(w, h, svgwriter,
filename),
+ width, height, image_dpi, RendererSVG(w, h, image_dpi,
svgwriter, filename),
bbox_inches_restore=_bbox_inches_restore)
self.figure.draw(renderer)
diff --git a/lib/matplotlib/tests/test_image.py
b/lib/matplotlib/tests/test_image.py
index 4556013..d11a0c9 100644
--- a/lib/matplotlib/tests/test_image.py
+++ b/lib/matplotlib/tests/test_image.py
@@ -160,6 +160,33 @@ def test_no_interpolation_origin():
ax = fig.add_subplot(212)
ax.imshow(np.arange(100).reshape((2, 50)), interpolation='none')
+
+@image_comparison(baseline_images=['rasterize_10dpi'],
extensions=['pdf','svg'], tol=1.5e-3, remove_text=True)
+def test_rasterize_dpi():
+ # This test should check rasterized rendering with high output resolution.
+ # It plots a rasterized line and a normal image with implot. So it will
catch
+ # when images end up in the wrong place in case of non-standard dpi
setting.
+ # Instead of high-res rasterization i use low-res. Therefor the fact that
the
+ # resolution is non-standard is is easily checked by image_comparison.
+ import numpy as np
+ import matplotlib.pyplot as plt
+
+ img = np.asarray([[1, 2], [3, 4]])
+
+ fig, axes = plt.subplots(1, 3, figsize = (3, 1))
+
+ axes[0].imshow(img)
+
+ axes[1].plot([0,1],[0,1], linewidth=20., rasterized=True)
+ axes[1].set(xlim = (0,1), ylim = (-1, 2))
+
+ axes[2].plot([0,1],[0,1], linewidth=20.)
+ axes[2].set(xlim = (0,1), ylim = (-1, 2))
+
+ rcParams['savefig.dpi'] = 10
+
+
+
if __name__=='__main__':
import nose
nose.runmodule(argv=['-s','--with-doctest'], exit=False)
--
1.7.4.1
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