When I view some transparent images in the iOS mobile app lightbox, the black lines in those images are indistinguishable from the background colour. The image previews are fine, it's just the lightbox that has issues.
The web app does this better, by using a grey background.
Unfortunately I don't have the original image for testing, but any image with transparency around black objects or lines should have the same issue.
Mobile app:
Web app:
Image without transparency:
When I view some transparent images in the iOS mobile app lightbox, the black lines in those images are indistinguishable from the background colour. The image previews are fine, it's just the lightbox that has issues.
The web app does this better, by using a grey background.
Unfortunately I don't have the original image for testing, but any image with transparency around black objects or lines should have the same issue.
Mobile app:
Web app:
Image without transparency: