Wanted: Progressive load of image files
Submitted by Toralf Lund
Another note from the "big files" department:
What would really do wonders for the support of the images I'm working on (multi-Gb TIFFs) is some kind of "progressive" image file load behaviour, i.e. the ability to suppress the read of data blocks from file until it is actually needed. This would mean transferring data from file to swap using a similar algorithm to the one used today to copy data from swap to tile cache. Actually, when viewing and anlysing files, but not changing their data, the swap wouldn't even be necessary; the data could be read directly from the file into the tile cache.
Of course, the total time taken to complete real image analysis and transform operations might be unchanged by this, but I think I would be able to work more efficiently because I wouldn't have to wait for several minutes for the image window to open (when startining up in 1:1 zoom mode - se bug 106960); I could have a quick glance at the data and start the desired operation (and have the opportunity to verify that the correct file was opened etc.) right away.
Also, implementing this kind of operation in a general way might be quite hard, but it would be trivial for formats like tiled TIFF (which is also what I'm mostly working on) where the data is already spit into smaller sections. It would probably be a good idea to keep the impelementation of the partial file read in the image format plugins, and have some kind of interaction when the file is opened to decide if it is supported at all, and for what block sizes.
Version: git master