Merge pull request #3381 from minrk/retina

enable 2x (retina) display

IPython/core/display.py

@@ -20,6 +20,7 b' Authors:'
 from __future__ import print_function
 
 import os
+import struct
 
 from IPython.utils.py3compat import string_types
 
@@ -471,6 +472,32 b' class Javascript(DisplayObject):'
 _PNG = b'\x89PNG\r\n\x1a\n'
 _JPEG = b'\xff\xd8'
 
+def _pngxy(data):
+    """read the (width, height) from a PNG header"""
+    ihdr = data.index(b'IHDR')
+    # next 8 bytes are width/height
+    w4h4 = data[ihdr+4:ihdr+12]
+    return struct.unpack('>ii', w4h4)
+
+def _jpegxy(data):
+    """read the (width, height) from a JPEG header"""
+    # adapted from http://www.64lines.com/jpeg-width-height
+    
+    idx = 4
+    while True:
+        block_size = struct.unpack('>H', data[idx:idx+2])[0]
+        idx = idx + block_size
+        if data[idx:idx+2] == b'\xFF\xC0':
+            # found Start of Frame
+            iSOF = idx
+            break
+        else:
+            # read another block
+            idx += 2
+
+    h, w = struct.unpack('>HH', data[iSOF+5:iSOF+9])
+    return w, h
+
 class Image(DisplayObject):
 
     _read_flags = 'rb'
@@ -478,7 +505,7 b' class Image(DisplayObject):'
     _FMT_PNG = u'png'
     _ACCEPTABLE_EMBEDDINGS = [_FMT_JPEG, _FMT_PNG]
 
-    def __init__(self, data=None, url=None, filename=None, format=u'png', embed=None, width=None, height=None):
+    def __init__(self, data=None, url=None, filename=None, format=u'png', embed=None, width=None, height=None, retina=False):
         """Create a display an PNG/JPEG image given raw data.
 
         When this object is returned by an expression or passed to the
@@ -512,6 +539,13 b' class Image(DisplayObject):'
             Width to which to constrain the image in html
         height : int
             Height to which to constrain the image in html
+        retina : bool
+            Automatically set the width and height to half of the measured
+            width and height.
+            This only works for embedded images because it reads the width/height
+            from image data.
+            For non-embedded images, you can just set the desired display width
+            and height directly.
 
         Examples
         --------
@@ -561,12 +595,32 b' class Image(DisplayObject):'
             raise ValueError("Cannot embed the '%s' image format" % (self.format))
         self.width = width
         self.height = height
+        self.retina = retina
         super(Image, self).__init__(data=data, url=url, filename=filename)
 
+        if retina:
+            self._retina_shape()
+    
+    def _retina_shape(self):
+        """load pixel-doubled width and height from image data"""
+        if not self.embed:
+            return
+        if self.format == 'png':
+            w, h = _pngxy(self.data)
+        elif self.format == 'jpeg':
+            w, h = _jpegxy(self.data)
+        else:
+            # retina only supports png
+            return
+        self.width = w // 2
+        self.height = h // 2
+
     def reload(self):
         """Reload the raw data from file or URL."""
         if self.embed:
             super(Image,self).reload()
+            if self.retina:
+                self._retina_shape()
 
     def _repr_html_(self):
         if not self.embed:

IPython/core/pylabtools.py

@@ -9,7 +9,7 b' Authors'
 """
 
 #-----------------------------------------------------------------------------
-#  Copyright (C) 2009-2011  The IPython Development Team
+#  Copyright (C) 2009  The IPython Development Team
 #
 #  Distributed under the terms of the BSD License.  The full license is in
 #  the file COPYING, distributed as part of this software.
@@ -22,6 +22,7 b' Authors'
 import sys
 from io import BytesIO
 
+from IPython.core.display import _pngxy
 from IPython.utils.decorators import flag_calls
 
 # If user specifies a GUI, that dictates the backend, otherwise we read the
@@ -90,6 +91,7 b' def figsize(sizex, sizey):'
 
 def print_figure(fig, fmt='png'):
     """Convert a figure to svg or png for inline display."""
+    from matplotlib import rcParams
     # When there's an empty figure, we shouldn't return anything, otherwise we
     # get big blank areas in the qt console.
     if not fig.axes and not fig.lines:
@@ -98,11 +100,21 b" def print_figure(fig, fmt='png'):"
     fc = fig.get_facecolor()
     ec = fig.get_edgecolor()
     bytes_io = BytesIO()
+    dpi = rcParams['savefig.dpi']
+    if fmt == 'retina':
+        dpi = dpi * 2
+        fmt = 'png'
     fig.canvas.print_figure(bytes_io, format=fmt, bbox_inches='tight',
-                            facecolor=fc, edgecolor=ec)
+                            facecolor=fc, edgecolor=ec, dpi=dpi)
     data = bytes_io.getvalue()
     return data
 
+def retina_figure(fig):
+    """format a figure as a pixel-doubled (retina) PNG"""
+    pngdata = print_figure(fig, fmt='retina')
+    w, h = _pngxy(pngdata)
+    metadata = dict(width=w//2, height=h//2)
+    return pngdata, metadata
 
 # We need a little factory function here to create the closure where
 # safe_execfile can live.
@@ -147,7 +159,7 b' def mpl_runner(safe_execfile):'
 
 
 def select_figure_format(shell, fmt):
-    """Select figure format for inline backend, either 'png' or 'svg'.
+    """Select figure format for inline backend, can be 'png', 'retina', or 'svg'.
 
     Using this method ensures only one figure format is active at a time.
     """
@@ -160,11 +172,14 b' def select_figure_format(shell, fmt):'
     if fmt=='png':
         svg_formatter.type_printers.pop(Figure, None)
         png_formatter.for_type(Figure, lambda fig: print_figure(fig, 'png'))
+    elif fmt in ('png2x', 'retina'):
+        svg_formatter.type_printers.pop(Figure, None)
+        png_formatter.for_type(Figure, retina_figure)
     elif fmt=='svg':
         png_formatter.type_printers.pop(Figure, None)
         svg_formatter.for_type(Figure, lambda fig: print_figure(fig, 'svg'))
     else:
-        raise ValueError("supported formats are: 'png', 'svg', not %r"%fmt)
+        raise ValueError("supported formats are: 'png', 'retina', 'svg', not %r" % fmt)
 
     # set the format to be used in the backend()
     backend_inline._figure_format = fmt

IPython/core/tests/test_display.py

@@ -22,6 +22,24 b' def test_image_size():'
     img = display.Image(url=thisurl)
     nt.assert_equal(u'<img src="%s"/>' % (thisurl), img._repr_html_())
 
+def test_retina_png():
+    here = os.path.dirname(__file__)
+    img = display.Image(os.path.join(here, "2x2.png"), retina=True)
+    nt.assert_equal(img.height, 1)
+    nt.assert_equal(img.width, 1)
+    data, md = img._repr_png_()
+    nt.assert_equal(md['width'], 1)
+    nt.assert_equal(md['height'], 1)
+
+def test_retina_jpeg():
+    here = os.path.dirname(__file__)
+    img = display.Image(os.path.join(here, "2x2.jpg"), retina=True)
+    nt.assert_equal(img.height, 1)
+    nt.assert_equal(img.width, 1)
+    data, md = img._repr_jpeg_()
+    nt.assert_equal(md['width'], 1)
+    nt.assert_equal(md['height'], 1)
+
 def test_image_filename_defaults():
     '''test format constraint, and validity of jpeg and png'''
     tpath = ipath.get_ipython_package_dir()

IPython/kernel/zmq/pylab/backend_inline.py

@@ -18,7 +18,7 b' from IPython.config.configurable import SingletonConfigurable'
 from IPython.core.display import display
 from IPython.core.displaypub import publish_display_data
 from IPython.core.pylabtools import print_figure, select_figure_format
-from IPython.utils.traitlets import Dict, Instance, CaselessStrEnum, CBool
+from IPython.utils.traitlets import Dict, Instance, CaselessStrEnum, Bool
 from IPython.utils.warn import warn
 
 #-----------------------------------------------------------------------------
@@ -56,7 +56,7 b' class InlineBackend(InlineBackendConfig):'
         inline backend."""
     )
 
-    figure_format = CaselessStrEnum(['svg', 'png'], default_value='png', config=True,
+    figure_format = CaselessStrEnum(['svg', 'png', 'retina'], default_value='png', config=True,
         help="The image format for figures with the inline backend.")
 
     def _figure_format_changed(self, name, old, new):
@@ -65,7 +65,7 b' class InlineBackend(InlineBackendConfig):'
         else:
             select_figure_format(self.shell, new)
     
-    close_figures = CBool(True, config=True,
+    close_figures = Bool(True, config=True,
         help="""Close all figures at the end of each cell.
         
         When True, ensures that each cell starts with no active figures, but it

setupbase.py

@@ -146,6 +146,7 b' def find_package_data():'
 
     package_data = {
         'IPython.config.profile' : ['README*', '*/*.py'],
+        'IPython.core.tests' : ['*.png', '*.jpg'],
         'IPython.testing' : ['*.txt'],
         'IPython.testing.plugin' : ['*.txt'],
         'IPython.html' : ['templates/*'] + static_data,