Editing dynamically selected portions of target images in a mask-based editing interface

A system comprising:

• a processing device;
• and
• a non-transitory computer-readable medium communicatively coupled to the processing device, wherein the processing device is configured to execute an image editing application stored in the non-transitory computer-readable medium and thereby perform operations comprising:
• receiving a selection state that (i) identifies a portion of a target image for display as a preview image in a mask-based editing interface and (ii) is described with a trimap of the target image, wherein the trimap includes trimap pixel sets respectively having (i) a first color identifying a foreground portion of the target image that is included in the preview image, (ii) a second color identifying a background portion of the target image, and (iii) a third color identifying trimap pixels as having an unknown class,
• storing the selection state in a quadmap of the target image, wherein the quadmap includes quadmap pixel sets respectively having the first color, the second color, the third color, and a fourth color that identifies quadmap pixels as protected pixels,
• applying an edge refinement operation that modifies a portion of the target image that includes pixels identified in the quadmap as having the unknown class,
• modifying, based on a selection input received via the mask-based editing interface, the selection state by creating a mask from both the applied edge refinement operation and pixels identified in the quadmap as the protected pixels, wherein the image editing application is configured for concurrently maintaining (i) the selection state and (ii) an edit state for the preview image that tracks an application of the edge refinement operation, and
• updating the preview image in the mask-based editing interface by rendering, as transparent, content from the target image that is outside a boundary of the mask.

A non-transitory computer-readable medium storing program code of an image editing application that is executable by a processing device to perform operations, the operations comprising:

• receiving a selection state that (i) identifies a portion of a target image for display as a preview image in a mask-based editing interface and (ii) is described with a trimap of the target image, wherein the trimap includes trimap pixel sets respectively having (i) a first color identifying a foreground portion of the target image that is included in the preview image, (ii) a second color identifying a background portion of the target image, and (iii) a third color identifying trimap pixels as having an unknown class;
• storing the selection state in a quadmap of the target image, wherein the quadmap includes quadmap pixel sets respectively having the first color, the second color, the third color, and a fourth color that identifies quadmap pixels as protected pixels;
• applying an edge refinement operation that modifies a portion of the target image that includes pixels identified in the quadmap as having the unknown class;
• modifying, based on a selection input received via the mask-based editing interface, the selection state by creating a mask from both the applied edge refinement operation and pixels identified in the quadmap as the protected pixels, wherein the image editing application concurrently maintains (i) the selection state and (ii) an edit state for the preview image that tracks an application of the edge refinement operation;
• and
• updating the preview image in the mask-based editing interface by rendering, as transparent, content from the target image that is outside a boundary of the mask.