Displaying partially downloaded images (while downloading)

[Dmitry Onoshko 0]

Are there any ready-to-use solutions for Delphi to display partially downloaded images? Like web browsers do over slow internet connections. I tried to load a few truncated versions of a PNG file into TImage (and, so, TPicture under the hood) and it fails on CRC check.

 

Since this stuff is highly format-dependent (say, displaying a partially downloaded BMP is quite easy, for PNG it’s quite tricky unless it has multiple IDAT chunks, while for JPEG with its different versions this might be a real pain to implement) implementing such a feature looks like a separate project. So, I wonder if anyone knows libraries where it’s already done.

 

(Of course, it’s not that critical for an application, and in most cases the image being downloaded can be replaced with a progress bar. I’m just curious.)