I've been re-ripping my entire collection to FLAC for archival purposes, and at the same time converting to 320kbps MP3 using Max. I've been adding JPEGs into the FLAC files using Tag&Rename (WinXP inside Virtual Box) which has been fine. I have noticed that when I convert to MP3, the size of the artwork increases dramatically in size - e.g. artwork at about 150kB (roughly 800x800px) in the FLAC becomes about 1.2MB in the subsequent MP3. The dimensions of the artwork do not increase, just the "file size". This can increase the artwork from about 1% of the MP3 file to almost 10% of the file - a considerable waste of space, and is requiring tedious manual intervention to remove the artwork, and re-add the original JPEGs again.
Does Max convert the artwork from JPEG to some other format when it does the conversion?
Is there something obvious I should be doing to prevent this?
Max converts the artwork into PNG format before saving.
I haven't done any comparisons so I don't know if PNG is really that much larger than JPEG, but it would seem a bit odd if there was that much of a difference in size.
Is there any chance of making the output format an option - or even allowing it to be copied from input file to output file without conversion?
With regard to the increase in file size, this is what I carried out as a quick experiment.
I've been taking artwork from allcdcovers.com (or scanning them myself when a CD is a bit more obscure). I downloaded the cover to Beautiful Garbage by Garbage (I'm up as far as G in my collection right now ) which was a 1421x1411 JPEG weighing in at 623kB. Using Preview, I opened the image, resized to 806x800 and saved it as a JPEG, which resulted in a file size of 311kB. I then opened the new image in Preview, and choose to Save As... a PNG. I changed no settings. The resultant file was 1.3MB in size.
At a guess I'd say you probably used Apple's Core Image framework to do your image conversion, which I'm sure Preview probably uses as well.