Fix use of "style_version" with GET (inline styles)

It took a lot of time to produce a testcase for this as the test
config was setting srid to 4326 but not changing geom column name
thus all tiles fetched by tests returned blank (ouch!)

test/support/assert.js

@@ -8,29 +8,35 @@ var exec = require('child_process').exec;
 
 var assert = module.exports = exports = require('assert');
 
-assert.imageEqualsFile = function(buffer, file_b, callback) {
+//
+// @param tol tolerated color distance as a percent over max channel value
+//            by default this is zero. For meaningful values, see
+//            http://www.imagemagick.org/script/command-line-options.php#metric
+//
+assert.imageEqualsFile = function(buffer, file_b, tol, callback) {
     if (!callback) callback = function(err) { if (err) throw err; };
     file_b = path.resolve(file_b);
-    var file_a = '/tmp/' + (Math.random() * 1e16);
+    var file_a = '/tmp/windshaft-test-image-test.png'; // + (Math.random() * 1e16); // TODO: make predictable 
     var err = fs.writeFileSync(file_a, buffer, 'binary');
     if (err) throw err;
 
-    exec('compare -metric PSNR "' + file_a + '" "' +
+    var fuzz = tol + '%';
+    exec('compare -fuzz ' + fuzz + ' -metric AE "' + file_a + '" "' +
             file_b + '" /dev/null', function(err, stdout, stderr) {
         if (err) {
             fs.unlinkSync(file_a);
             callback(err);
         } else {
             stderr = stderr.trim();
-            if (stderr === 'inf') {
-                fs.unlinkSync(file_a);
-                callback(null);
+            var similarity = parseFloat(stderr);
+            if ( similarity > 0 ) {
+              var err = new Error('Images not equal(' + similarity + '): ' +
+                      file_a  + '    ' + file_b);
+              err.similarity = similarity;
+              callback(err);
             } else {
-                var similarity = parseFloat(stderr);
-                var err = new Error('Images not equal(' + similarity + '): ' +
-                        file_a  + '    ' + file_b);
-                err.similarity = similarity;
-                callback(err);
+              fs.unlinkSync(file_a);
+              callback(null);
             }
         }
     });