You heard this in relation to how you should store your originals. If your camera doesn’t make Raw or TIFF or something non-desctructive like that as its native file format, then your very first step after downloading the JPEG is to convert it to a 24-bt PNG. Do that and then never touch the JPEG again. Place the PNG in your Freeway layout in any non-pass-through graphic container you like. Freeway will convert it to JPEG for you, and all will be well with the world.
So why shouldn’t you JPEG a JPEG? JPEG is a lossy compression algorithm. It works by analyzing the photo data in 32px-square “superblocks”, finding those that it can reduce to a single expression or a flat color, and throws out all the other picture data in that block. Then it moves on to the next. Each time it does this, it also horses around with the edges of high-contrast items, producing a similar artifact to aggressive sharpening (in Photoshop) on a low resolution image.
Ever see “crawly things” in the sky next to a dark object like a tree? That’s a classic JPEG artifact.
So combine these features together (the sharpening-like effect, which tries to enhance the boundary between high contrast areas, and the random noise brought in by the superblock treatment, and you end up with an escalating recipe for disaster. Save a JPEG as a JPEG enough generations, and it will not only look worse each time, it will also start to get slightly larger, as that noise (indistinguishable from detail to an algorithm) has to be sharpened more and more each time, which means fewer large areas of color to be expressed as a tidy algorithm.
JPEG is a fine delivery medium for the Web, but as an archival format, you could only do worse with GIF.
Walter
On May 16, 2013, at 7:58 PM, Artivideo wrote:
I read somewhere that in Freeway it is better to use png files than jpg files. So what is your advice ?
freewaytalk mailing list
email@hidden
Update your subscriptions at:
http://freewaytalk.net/person/options