JPEG and PNG

samson123

New Member
JPEG files are compressed but support “true color” (24 bit) and are the preferred format for photographs where image quality matters. JPEG supports a progressive format that allows for an almost immediate image that will improve in quality as the rest of it loads. Unlike a GIF file, the compression for JPEG files can be controlled by the web designer, which allows for different levels of picture quality and file size. All browsers can display GIF files. JPEG Advantages: Large compression ration mean faster download speeds, Produces excellent quality for photographs and complex drawings and Supports 24-bit color.

PNG is a fairly recent format that was introduced as an alternative to GIF files. PNG supports up to 24 bit color, transparency, interlacing and can hold a short text description of the image’s content for use by search engines. Unfortunately, most browsers do not support PNG and the ones that do support it, don’t support all of its features yet. But that will change in the future. PNG Advantages: Overcomes the 8-bit color limitation of GIF, Allows text description of the image for search engine use, Supports transparency and Diagrams look better than they do in JPEG.

Most web graphics are raster images or bitmaps, which consist of a grid of colored pixels. Drawing and illustrations should be created as vector graphics which consist of mathematical descriptions of each element that makes up the lines shapes and color of the image. Vector graphics are created by drawing programs such as Adobe Illustrator and Macromedia Freehand and are the graphic artists choice for creating drawings. Vector graphics must be converted to either GIF, JPEG OR PNG format to be used on a web page.

Website Designers could choose either the GIF or JPEG format for most uses. But, since the file size of a GIF is usually small than the file size of a JPEG, most web designers will use the GIF format for backgrounds, boxed, frames and any other graphical element that look fine using 8-bit color. Most designers will select the JPEG format for photographs and illustrations where the compression doesn’t compromise the visual quality of the image. As PNG becomes fully supported by most web browsers, it will probably replace GIF as the web designer’s choice for non-photographic page elements. However, GIF will still be used for animation. GIF and JPEG are universally supported and the web designer’s choice is determined by the graphic element being used.
 
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adx

New Member
Unfortunately, most browsers do not support PNG and the ones that do support it, don’t support all of its features yet.

That's quite the nice summary. You obviously know you stuff! If I could add one thing from a designers perspective it would be that PNG images are well supported as long as you don't use transparency, which will render as crazy stripes in browsers prior to IE7.

I know I'm basically repeating exactly what you said, but I thought I'd clarify a bit. Is there a specific reason for the transparency issue, do you know? I always thought that was a little strange!
 

cmjvulavala

New Member
Just something to add to this thread... there is also a newer alternative to GIF that supports animation. Its very similar to PNG except it adds support for animation as well. Its known as MNG (Multiple-Image Network Graphics)... more about MNG at :http://www.libpng.org/pub/mng/
 

tim84

New Member
Agree with conor. I usually save my large Bitmaps images as PNG files just to shrink the size while also retaining the quality.
 

ashgray2

New Member
JPEG is a standardised image compression mechanism. JPEG is designed for compressing either full-colour (24 bit) or grey-scale digital images of "natural" (real-world) scenes.

JPEG is "lossy", meaning that the image you get out of decompression isn't quite identical to what you originally put in. The algorithm achieves much of its compression by exploiting known limitation of the human eye, notably the fact that small colour details aren't perceived as well as small details of light-and-dark. Thus, JPEG is intended for compressing images that will be looked at by humans.

PNG is superior to GIF in that it has better compression and supports millions of colours.
 
When ever i scan photos into my computer, and then try to put them onto photobucket or myspace they wont work it says i need to chnage them into gif, jpg, jpeg, png, bmp files. I dont know how please help?
 

kidsko

New Member
Depends on what your looking to get across in your designs and if your concerned about server load. Obviously you have people who will put images of 1.5megs up which makes absolutely no sense at all, but that just shows how experienced they are. Personally I try and scale everything down in PNG without any loss of colors, because it allows for good compression and reduction and size.
 
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