I have a strange issue with large, off-color "squares" appearing when I preview a PNG with halftones on a transparent background. This doesn't happen with all images (so far, I've only had the issue with about 4 out of 60 or so images) and this is exclusively when the halftones occur on a transparent background. Here's a small example:
The image on the left has a transparent background, while the image on the right is on top of a small white square. Other than that they are identical. Here's what it looks like when opened in photoshop:
I believe these are some strange artifact caused by the viewing program (e.g., Windows Photo Gallery) and not an integral part of the image, since if you zoom in they "disappear."
I believe this is an issue only with fairly large images (in this case, 13x16" at 300 dpi with halftones at 55 LPI). My main problem with this is that if I upload the images to a site (dA, RB, S6, etc.), the weird squares appear there as well. I have tried reducing the halftones to as low as 30 LPI, but to no avail. Does anyone know what might be causing this issue and how remedy it?