I was recently reading about progressive image loading, but I was disappointed with the fact that a separate thumbnail was being used for the initial "blurry" rendering, as this creates additional data for the client to download.
My understanding is that existing raster image formats are organized by coordinates (left to right, top to bottom). It seems to me that the image data could be ordered based on a downscaling algorithm. This would allow the client to automatically display a progressive representation of the image as it downloaded the data.
Are there any existing file formats and/or methods that allow progressive image loading without creating separate thumbnails for each step of resolution?
Did some more research. What I'm looking for is called interlacing.
Existing interlacing approaches aren't exactly what I had in mind, but it is definitely the same concept.