A design image is transformed into a projection design image comprising the design image as it will appear when projected onto a physical 3-dimensional (3-D) curved object. In an embodiment, pixels of the design image are mapped into corresponding mapped pixels in a projection design image according to how the design image will appear in a flattened image of the design projected or printed onto the object having 3-dimension curves. The projection design image may be combined with a product image of the object having 3-dimension curves to generate a customized product image of the object having 3-dimension curves incorporating the design image. The customized product image is displayed to a user when customizing a product with a design to ensure that the user understands how the physical product will appear when the design is printed or projected onto the physical product.