The present disclosure includes systems and techniques relating to processing of high resolution images, such as digital painting on high resolution images. In general, one aspect of the subject matter described in this specification can be embodied in a method that includes receiving input defining a modification to a target image; determining, at a first processor, a low resolution proxy result of the modification applied to the target image; determining, at a second processor, a higher resolution result of the modification applied to the target image; displaying the low resolution proxy result before completion of the determining at the second processor; and updating the displayed low resolution proxy result with the higher resolution result. Other embodiments of this aspect include corresponding systems, apparatus, and computer program products.