Warn on old crisp-edges value

lib/hacks/image-rendering.coffee

@@ -27,4 +27,12 @@ class ImageRendering extends Declaration
   normalize: (prop) ->
     'image-rendering'
 
+  # Warn on old value
+  process: (node, result) ->
+    if @name == 'image-rendering' and node.value == 'crisp-edges'
+      result.warn('There is no browsers with crisp-edges rendering support.' +
+                  'Maybe you mean pixelated?', node: node)
+
+    super
+
 module.exports = ImageRendering

lib/processor.coffee

@@ -38,7 +38,7 @@ class Processor
 
       prefix = @prefixes.add[decl.prop]
       if prefix and prefix.prefixes
-        prefix.process(decl) if not @disabled(decl)
+        prefix.process(decl, result) if not @disabled(decl)
 
     # Values
     css.eachDecl (decl) =>

test/autoprefixer.coffee

@@ -189,7 +189,6 @@ describe 'Autoprefixer', ->
     it 'ignores some 3D transforms',    -> test('3d-transform')
     it 'supports background-size',      -> test('background-size')
     it 'supports background-clip',      -> test('background-clip')
-    it 'supports image-rendering',      -> test('image-rendering')
     it 'supports logical properties',   -> test('logical')
     it 'supports appearance',           -> test('appearance')
 
@@ -203,6 +202,16 @@ describe 'Autoprefixer', ->
         ['autoprefixer: <css input>:1:1: Selector ::placeholder is ' +
          'unofficial. Use :placeholder-shown instead.'])
 
+    it 'supports image-rendering', ->
+      input  = read('image-rendering')
+      output = read('image-rendering.out')
+      result = postcss([prefixer('image-rendering')]).process(input)
+
+      result.css.should.eql(output)
+      result.warnings().map( (i) -> i.toString() ).should.eql(
+        ['autoprefixer: <css input>:2:5: There is no browsers with ' +
+         'crisp-edges rendering support.Maybe you mean pixelated?'])
+
     it 'warn on old flexbox display', ->
       result = postcss([flexboxer]).process('a{ display: box; }')
       result.css.should.eql('a{ display: box; }')