The current implementation has several limitations. Entire blocks in redacted regions are processed rather than attempting to decompress and redact only subparts of blocks, a theoretical possibility described earlier. In practice, this has been sufficient, since the identifying information is usually located far enough from the diagnostic information in the image for this not to matter. Further, partial block redaction might render the block vulnerable to recovery methods such as those described by Zhong-Yang Ho.39 Using the DC coefficient difference value unchanged results in a patchwork of color blocks rather than a single value (such as black) for the redacted blocks. Conceivably, if the offending text was rendered in a very large font relative to the block size, then the redaction might fail to obscure the text, but this has not proven to be an issue in practice, since the font strokes are usually of the order of a single pixel in width. If redaction of areas other than text is required, such as of facial features, particularly in high-resolution images, the decision not to change the DC coefficient to a single value may need to be revisited. Only the 8-bit per component JPEG process is currently implemented since it is the most common format in which images with burned-in text are encountered. JPEG also defines an extended, 12-bit, process, which is sometimes used for compressing CT and MR and X-ray images, but in general, these do not contain burned-in text; extension of the implementation to support greater component precision would be very straightforward, particularly since only the entropy coded is affected and a higher precision DCT is not needed.