+webscouter. Posted June 11, 2007 Share Posted June 11, 2007 During an update of my profile I created a PNG map from the Bank of Frank site. It looks nice and crisp. The JPG of the same map looks awful no matter how I convert it. Are there any plans to add the ability to upload PNG to a log instead of just JPG? I did a search but only found references to using PNG in the forums. PNG Image JPG Image Link to comment
+The Cheeseheads Posted June 11, 2007 Share Posted June 11, 2007 I'm going to guess that image uploading is mainly intended for photos, and as such, JPEG compression is ideal to keep image sizes down while keeping the picture looking nice. Link to comment
+TotemLake Posted June 11, 2007 Share Posted June 11, 2007 I'm going to guess that image uploading is mainly intended for photos, and as such, JPEG compression is ideal to keep image sizes down while keeping the picture looking nice. The problem with JPEGs is they do lose their quality over time being a lossy format. It would be nice to be able to use PNG because it is lossless which means the quality doesn't degrade over time. Link to comment
+StarBrand Posted June 11, 2007 Share Posted June 11, 2007 The problem with JPEGs is they do lose their quality over time being a lossy format. huh!! It loses quality when saved as a JPG but if it is never opened and resaved again - The file retains the quality it had when originally saved. Even so, .JPG with a little tweaking saves just about any file with virtually no perceptual loss of quality. Link to comment
+admo1972 Posted June 11, 2007 Share Posted June 11, 2007 I agree to keep png out of it. 90% of the time, the jpg and the png are perceptually identical, and 90% of the remaining 10% it is only slight color variations that is discernible. For an image that is not intended to be resaved over and over again, jpg is almost always best. Link to comment
+Driver Carries Cache Posted June 11, 2007 Share Posted June 11, 2007 Internet Explorer (versions 4-6) have issues with PNG that can sometimes lead to a browser crash. I can say that as a web developer I would love to see PNG become more well supported. And yes, a PNG file of equal size will trounce the image quality of a JPG and PNG is designed to support transparency which makes the use of GIF files for that purpose less likely as well. DCC Link to comment
+klossner Posted June 11, 2007 Share Posted June 11, 2007 I've had some experience in this area as part of my day job. JPEG stands for Joint Photographic Experts Group. The file format is designed for photographs and only for photographs. The compression method it uses is good at preserving the information the eye sees for "continuous tone" images only. If you apply it to a non-photographic image with sharp boundaries between objects, such as a text file or an outline-graphics file like webscouter's map, the result is pretty awful. PNG, on the other hand, is not necessarily lossless. If you use "indexed" color, then the colors in your image are quantized to the palette. If you reduce the bit depth per channel, you discard the less significant bits of each pixel. If you do neither of these things, your file is unreasonably large. I've seen photographic files using PNG's lossless ("Flate") compression that were ten times larger than the corresponding JPEG file. I've seen photos compressed to the same size in PNG and JPEG; the PNG image looked atrocious. Bottom line is you should use JPEGs for photos only. For outline graphics like this, use PNG or GIF. Link to comment
+conradv Posted June 11, 2007 Share Posted June 11, 2007 (edited) The main purpose of PNG was to replace GIF (and TIFF LZW). PNG not only is lossless, it is open format and royalty free. I archive all of my digital photos as PNG. Also, a PNG is aobut 75% of the size of a TIFF image. I do agree though that JPG is probably the best way to go for web pages, as a JPG is about 16% of the size of a PNG, but with today's huge storage capability, I would never consider archiving anything as a JPG. Edited June 11, 2007 by conradv Link to comment
+Prime Suspect Posted June 11, 2007 Share Posted June 11, 2007 I'm going to guess that image uploading is mainly intended for photos, and as such, JPEG compression is ideal to keep image sizes down while keeping the picture looking nice. The problem with JPEGs is they do lose their quality over time being a lossy format. It would be nice to be able to use PNG because it is lossless which means the quality doesn't degrade over time. The don't degrade over time. They degrade over edit/compression generations. Link to comment
+benh57 Posted June 12, 2007 Share Posted June 12, 2007 99.9% of users will still use JPG. In all likelihood, you will never see a log with a PNG on it. I don't get why anyone would object to this. Link to comment
+klossner Posted June 12, 2007 Share Posted June 12, 2007 99.9% of users will still use JPG. In all likelihood, you will never see a log with a PNG on it.That's because, if you upload a PNG or GIF file, the web site silently converts it to a JPEG. I don't get why anyone would object to this.Here's an example of extreme JPEG compression applied to a non-contone image. Notice the halo effects. Link to comment
+StarBrand Posted June 12, 2007 Share Posted June 12, 2007 pretty darn good for a 10k file. How big is the .png? Link to comment
+Shorelander Posted June 12, 2007 Share Posted June 12, 2007 (edited) The key is for geometric shapes - like outline maps of the United States, as the original poster indicated - PNGs will be crisper and of equal or smaller size. Here's an example I whipped up hosted on my Flickr account: Note that the PNG is smaller than the JPG. It's of better quality, as you can tell by zooming in: (Note that I accidentally reversed the positions of the PNG and JPG between the two. The captions are correct. EDIT: Alas, flickr JPG-ified them. The relative quality in the zoomed version still applies, though. Edited June 12, 2007 by Shorelander Link to comment
Recommended Posts