Merge pull request #12864 from blois/alt_text

Allow specifying alt text for IPython.display.Image.

IPython/core/display.py

@@ -6,6 +6,7 b''
 
 
 from binascii import b2a_base64, hexlify
+import html
 import json
 import mimetypes
 import os
@@ -800,9 +801,20 b' class Image(DisplayObject):'
         _FMT_GIF: 'image/gif',
     }
 
-    def __init__(self, data=None, url=None, filename=None, format=None,
-                 embed=None, width=None, height=None, retina=False,
-                 unconfined=False, metadata=None):
+    def __init__(
+        self,
+        data=None,
+        url=None,
+        filename=None,
+        format=None,
+        embed=None,
+        width=None,
+        height=None,
+        retina=False,
+        unconfined=False,
+        metadata=None,
+        alt=None,
+    ):
         """Create a PNG/JPEG/GIF image object given raw data.
 
         When this object is returned by an input cell or passed to the
@@ -847,6 +859,8 b' class Image(DisplayObject):'
             Set unconfined=True to disable max-width confinement of the image.
         metadata : dict
             Specify extra metadata to attach to the image.
+        alt : unicode
+            Alternative text for the image, for use by screen readers.
 
         Examples
         --------
@@ -924,6 +938,7 b' class Image(DisplayObject):'
         self.height = height
         self.retina = retina
         self.unconfined = unconfined
+        self.alt = alt
         super(Image, self).__init__(data=data, url=url, filename=filename,
                 metadata=metadata)
 
@@ -933,6 +948,9 b' class Image(DisplayObject):'
         if self.height is None and self.metadata.get('height', {}):
             self.height = metadata['height']
 
+        if self.alt is None and self.metadata.get("alt", {}):
+            self.alt = metadata["alt"]
+
         if retina:
             self._retina_shape()
 
@@ -962,18 +980,21 b' class Image(DisplayObject):'
 
     def _repr_html_(self):
         if not self.embed:
-            width = height = klass = ''
+            width = height = klass = alt = ""
             if self.width:
                 width = ' width="%d"' % self.width
             if self.height:
                 height = ' height="%d"' % self.height
             if self.unconfined:
                 klass = ' class="unconfined"'
-            return u'<img src="{url}"{width}{height}{klass}/>'.format(
+            if self.alt:
+                alt = ' alt="%s"' % html.escape(self.alt)
+            return '<img src="{url}"{width}{height}{klass}{alt}/>'.format(
                 url=self.url,
                 width=width,
                 height=height,
                 klass=klass,
+                alt=alt,
             )
 
     def _repr_mimebundle_(self, include=None, exclude=None):
@@ -1006,6 +1027,8 b' class Image(DisplayObject):'
             md['height'] = self.height
         if self.unconfined:
             md['unconfined'] = self.unconfined
+        if self.alt:
+            md["alt"] = self.alt
         if md or always_both:
             return b64_data, md
         else:

IPython/core/tests/test_display.py

@@ -94,9 +94,9 b' def test_embed_svg_url():'
 
         if args[0] == url:
             return MockResponse(svg_data)
-        elif args[0] == url + 'z':          
+        elif args[0] == url + "z":
             ret= MockResponse(gzip_svg)
-            ret.headers['content-encoding']= 'gzip'
+            ret.headers["content-encoding"] = "gzip"
             return ret
         return MockResponse(None)
 
@@ -460,6 +460,31 b' def test_display_handle():'
     })
 
 
+def test_image_alt_tag():
+    """Simple test for display.Image(args, alt=x,)"""
+    thisurl = "http://example.com/image.png"
+    img = display.Image(url=thisurl, alt="an image")
+    nt.assert_equal(u'<img src="%s" alt="an image"/>' % (thisurl), img._repr_html_())
+    img = display.Image(url=thisurl, unconfined=True, alt="an image")
+    nt.assert_equal(
+        u'<img src="%s" class="unconfined" alt="an image"/>' % (thisurl),
+        img._repr_html_(),
+    )
+    img = display.Image(url=thisurl, alt='>"& <')
+    nt.assert_equal(
+        u'<img src="%s" alt="&gt;&quot;&amp; &lt;"/>' % (thisurl), img._repr_html_()
+    )
+
+    img = display.Image(url=thisurl, metadata={"alt": "an image"})
+    nt.assert_equal(img.alt, "an image")
+
+    here = os.path.dirname(__file__)
+    img = display.Image(os.path.join(here, "2x2.png"), alt="an image")
+    nt.assert_equal(img.alt, "an image")
+    _, md = img._repr_png_()
+    nt.assert_equal(md["alt"], "an image")
+
+
 @nt.raises(FileNotFoundError)
 def test_image_bad_filename_raises_proper_exception():
     display.Image("/this/file/does/not/exist/")._repr_png_()