new Object property strokeUniform allows the stroke width to always stay the same width as object scales

src/mixins/object_geometry.mixin.js

@@ -592,8 +592,16 @@
       if (skewX === 0 && skewY === 0) {
         return { x: dimensions.x * this.scaleX, y: dimensions.y * this.scaleY };
       }
-      var dimX = dimensions.x / 2, dimY = dimensions.y / 2,
-          points = [
+      var dimX, dimY;
+      if (this.strokeUniform) {
+        dimX = this.width / 2;
+        dimY = this.width / 2;
+      }
+      else {
+        dimX = dimensions.x / 2;
+        dimY = dimensions.y / 2;
+      }
+      var points = [
             {
               x: -dimX,
               y: -dimY
@@ -616,7 +624,10 @@
         points[i] = fabric.util.transformPoint(points[i], transformMatrix);
       }
       bbox = fabric.util.makeBoundingBoxFromPoints(points);
-      return { x: bbox.width, y: bbox.height };
+      return this.strokeUniform ?
+        { x: bbox.width + this.strokeWidth, y: bbox.height + this.strokeWidth }
+        :
+        { x: bbox.width, y: bbox.height };
     },
 
     /*

src/shapes/object.class.js

@@ -560,6 +560,16 @@
      */
     noScaleCache:              true,
 
+    /**
+     * When `false`, the stoke width will scale with the object.
+     * When `true`, the stroke will always match the exact pixel size entered for stroke width.
+     * default to false
+     * since 2.5.1
+     * @type Boolean
+     * @default false
+     */
+    strokeUniform:              false,
+
     /**
      * When set to `true`, object's cache will be rerendered next render call.
      * since 1.7.0
@@ -1323,6 +1333,9 @@
       else {
         alternative && alternative(ctx);
       }
+      if (this.strokeUniform) {
+        ctx.setLineDash(ctx.getLineDash().map(function(value) { return value * ctx.lineWidth; }));
+      }
     },
 
     /**
@@ -1460,6 +1473,9 @@
       }
 
       ctx.save();
+      if (this.strokeUniform) {
+        ctx.scale(1 / this.scaleX, 1 / this.scaleY);
+      }
       this._setLineDash(ctx, this.strokeDashArray, this._renderDashedStroke);
       this._applyPatternGradientTransform(ctx, this.stroke);
       ctx.stroke();