Target image file sizes? Options

[d_headshot]

Let's say I had a 1000x1000 pixel jpeg image used for album art. What would be the minimum filesize I would need in order to have the best quality possible? At least 1MB? How would I also calculate that for 600x600?

This post has been edited by d_headshot: Jun 2 2011, 23:48

[Robertina]

If your main concern is about picture quality you should be aware that JPG is a lossy file format. And the file sizes needed by JPGs depend - amongst other things - on the quality level setting you choose in your image processing program as well as on the content, structure and complexity of your source files: some Album Covers simply consist of the album's name on an unicoloured background, others are rich in details, why the latter target images would require a lot more storage space. Wikipedia says

JPEG typically achieves 10:1 compression with little perceptible loss in image quality

but they miss to mention for which source file formats this is true: Raw images such as bmp can of course be higher compressed than a JPG, that is already compressed.

Perhaps you want to try IrfanView. Its batch processing function allows to play easily around with different target file formats and quality levels, in order to find out which file sizes you would have to expect with your individual files. There are also some image size calculators as stand-alone programs available but I think they are not necessarily trustworthy.

[Andavari]

While IrfanView is a nice image viewer which I've used for umpteen years I however personally avoid it's JPG saving like the plague! The reason being some hardware devices can't read IrfanView saved JPG's!

If wanting to figure out what quality to save JPG's, and if you use Windows give Paint.NET a try since it allows you to save at a quality, the default is 95%. For "folder.jpg" files I try to shoot for 20KB which could mean reducing the quality percentage to 75% but I never go under 75%.

The filesize however is unknown as it depends solely upon the image you're saving, i.e.; if it's complex, has allot of colours which won't exactly compress very well which will in turn mean saving at a higher quality percentage if you wish to retain image quality.

For myself as a general rule of thumb when saving a large sized cover.jpg (for re-printing should the need arise) I save at 98% quality percentage.

[Robertina]

While IrfanView is a nice image viewer which I've used for umpteen years I however personally avoid it's JPG saving like the plague! The reason being some hardware devices can't read IrfanView saved JPG's!

I don't want to defend IrfanView against legitimate criticism, but perhaps you saved your pictures as progressive JPGs or as JPEG 2000? These formats are less compatible.

If wanting to figure out what quality to save JPG's, and if you use Windows give Paint.NET a try since it allows you to save at a quality, the default is 95%. For "folder.jpg" files I try to shoot for 20KB which could mean reducing the quality percentage to 75% but I never go under 75%.

If I don't misunderstand you in this (I don't use Paint.NET), these functions are supported by IrfanView as well. You just have to tick the option "Show options dialog" in the "Save as" dialog.

[Andavari]

perhaps you saved your pictures as progressive JPGs or as JPEG 2000? These formats are less compatible.

Nope, just saved as straight up standard JPGs which Microsoft Paint can even read after IrfanView saves them. Note that I've tried IrfanViews JPGs for several years and many versions but no luck with some hardware devices that deem them corrupt. I can literally take those same JPGs and very lossy re-save them with Microsoft Paint or Paint.NET with them being read without problems in effected hardware.