SVG的免费转换插件 - 创建占位符元素

I'm trying to create html5 collage editor, where you can edit images in similar way to one you see in Word (cropping images instead of scaling them when dragging edges, being able to drag/rotate/scale images inside free transform area (so sort of placeholder funcionality), etc.). It means we need using SVG and clipping/masking, and binding position of free transform elements to those masks/clippings. Whole generated SVG should later be scalable for print dimensions (but that is not the issue here).I'm trying to create html5 collage editor, wher