Elimination of artifacts from lossy encoding of digital images by color channel expansion

A computer system comprising:

• one or more processors;
• one or more non-transitory computer-readable media storing instructions which, when executed by the one or more processors, cause the one or more processors to perform:
• receiving a digital image file comprising a plurality of digital channel datasets corresponding to a plurality of image channels, wherein the digital image file includes an image region comprising pixels that encode image data and a non-image region comprising pixels that do not encode image data;
• determining a boundary for the image region;
• for each channel in the plurality of channels, generating a buffer region by:
• using the digital channel datasets, identifying a plurality of pixels along the boundary;
• for each pixel of the plurality of pixels, copying the pixel one or more times outward from the image region into pixels of the non-image region adjacent to the boundary, to reduce artifact creation along the boundary;
• and
• storing a modified digital image file that includes the buffer region.