new plugin converting some basic shapes to path

.svgo.yml

@@ -31,6 +31,7 @@ plugins:
   - cleanupEnableBackground
   - removeHiddenElems
   - removeEmptyText
+  - convertShapeToPath
   - moveElemsAttrsToGroup
   - moveGroupAttrsToElems
   - collapseGroups

plugins/convertShapeToPath.js

@@ -0,0 +1,102 @@
+'use strict';
+
+exports.type = 'perItem';
+
+exports.active = true;
+
+var empty = { value: 0 },
+    regSeparator = /\s+,?\s*|,\s*/;
+
+/**
+ * Converts basic shape to more compact path.
+ * It also allows further optimizations like
+ * combining paths with similar attributes.
+ *
+ * @see http://www.w3.org/TR/SVG/shapes.html
+ *
+ * @param {Object} item current iteration item
+ * @param {Object} params plugin params
+ * @return {Boolean} if false, item will be filtered out
+ *
+ * @author Lev Solntsev
+ */
+exports.fn = function(item, params) {
+
+    if (
+        item.isElem('rect') &&
+        item.hasAttr('width') &&
+        item.hasAttr('height') &&
+        !item.hasAttr('rx') &&
+        !item.hasAttr('ry')
+    ) {
+
+        var x = +(item.attr('x') || empty).value,
+            y = +(item.attr('y') || empty).value,
+            width  = +item.attr('width').value,
+            height = +item.attr('height').value;
+
+            // Values like '100%' compute to NaN, thus running after
+            // cleanupNumericValues when 'px' units has already been removed.
+            // TODO: Calculate sizes from % and non-px units if possible.
+        if (isNaN(x - y + width - height)) return;
+
+        var pathData =
+            'M' + x + ' ' + y +
+            'H' + (x + width) +
+            'V' + (y + height) +
+            'H' + x +
+            'z';
+
+        item.addAttr({
+                name: 'd',
+                value: pathData,
+                prefix: '',
+                local: 'd'
+            });
+
+        ['x', 'y', 'width', 'height'].forEach(function(attr){ item.removeAttr(attr) });
+        item.elem = item.local = 'path';
+
+    } else if (item.isElem('line')) {
+
+        var x1 = +(item.attr('x1') || empty).value,
+            y1 = +(item.attr('y1') || empty).value,
+            x2 = +(item.attr('x2') || empty).value,
+            y2 = +(item.attr('y2') || empty).value;
+        if (isNaN(x1 - y1 + x2 - y2)) return;
+
+        item.addAttr({
+                name: 'd',
+                value: 'M' + x1 + ' ' + y1 + 'L' + x2 + ' ' + y2,
+                prefix: '',
+                local: 'd'
+            });
+
+        ['x1', 'y1', 'x2', 'y2'].forEach(function(attr){ item.removeAttr(attr) });
+        item.elem = item.local = 'path';
+
+    } else if ((
+            item.isElem('polyline') ||
+            item.isElem('polygon')
+        ) &&
+        item.hasAttr('points')
+    ) {
+
+        var coords = item.attr('points').value.split(regSeparator);
+        if (coords.length < 4) return false;
+
+        item.addAttr({
+                name: 'd',
+                value: 'M' + coords.slice(0,2).join(' ') +
+                       'L' + coords.slice(2).join(' ') +
+                       (item.isElem('polygon') ? 'z' : ''),
+                prefix: '',
+                local: 'd'
+            });
+
+        item.removeAttr('points');
+        item.elem = item.local = 'path';
+
+    }
+
+};