`color-rendering` CSS property and SVG attribute was removed

[carlosame]

The color-rendering CSS property (and the corresponding SVG attribute) was removed from the SVG specification (w3c/svgwg#647).

Both EchoSVG and Batik are using it and I wondered if it would make sense to default to optimizeQuality here.

Experiment

I applied the following patch to CSSUtilities in the css module:

@@ -480,29 +480,28 @@ public abstract class CSSUtilities implements CSSConstants, ErrorConstants, XMLC
 	 * @param hints a RenderingHints to fill, or null.
 	 */
 	public static RenderingHints convertColorRendering(Element e, RenderingHints hints) {
 		Value v = getComputedStyle(e, SVGCSSEngine.COLOR_RENDERING_INDEX);
 		String s = v.getIdentifierValue();
-		int len = s.length();
-		if ((len == 4) && (s.charAt(0) == 'a')) // auto
-			return hints;
-		if (len < 13)
-			return hints; // Unknown.
 
-		if (hints == null)
+		if (hints == null) {
 			hints = new RenderingHints(null);
+		}
 
-		switch (s.charAt(8)) {
-		case 's': // optimizeSpeed
+		if (s.length() == 13 && s.charAt(8) == 's') { // optimizeSpeed
 			hints.put(RenderingHints.KEY_COLOR_RENDERING, RenderingHints.VALUE_COLOR_RENDER_SPEED);
-			hints.put(RenderingHints.KEY_ALPHA_INTERPOLATION, RenderingHints.VALUE_ALPHA_INTERPOLATION_SPEED);
-			break;
-		case 'q': // optimizeQuality
-			hints.put(RenderingHints.KEY_COLOR_RENDERING, RenderingHints.VALUE_COLOR_RENDER_QUALITY);
-			hints.put(RenderingHints.KEY_ALPHA_INTERPOLATION, RenderingHints.VALUE_ALPHA_INTERPOLATION_QUALITY);
-			break;
+			hints.put(RenderingHints.KEY_ALPHA_INTERPOLATION,
+					RenderingHints.VALUE_ALPHA_INTERPOLATION_SPEED);
+			return hints;
 		}
+		// auto, optimizeQuality or invalid
+
+		// In this implementation, optimizeQuality is equivalent to auto or invalid
+		hints.put(RenderingHints.KEY_COLOR_RENDERING, RenderingHints.VALUE_COLOR_RENDER_QUALITY);
+		hints.put(RenderingHints.KEY_ALPHA_INTERPOLATION,
+				RenderingHints.VALUE_ALPHA_INTERPOLATION_QUALITY);
+
 		return hints;
 	}
 
 	/////////////////////////////////////////////////////////////////////////
 	// 'display'

and then ran the tests.

Results

44 tests failed (rendering variations were detected), with many images looking better (e.g. radial gradients) while others don't. In the following images, left is the current rendering, right is with the patch:

gradientLimit

linearGradientRepeat

paintType

radialGradient

radialGradient2

The gradientLimit rendering doesn't look good and I wonder if that could be considered a bug in the JDK; the left solid line in the paintType squares looks like a bug as well.

I have no plans to merge the patch but feedback would be appreciated, if anyone is familiar with the issue.