Several browsers support the attributes WIDTH and
HEIGHT for tags like <IMG>. If you know the
exact size of your image, you can tell it the browser. This might
speed up the layout-engine, because the browser doesn't have to
wait for the image to be transfered or needs to re-layout the page
after the transfer.
As you usually don't know the exact size of your images, let your
stupid computer handle that tricky task by enabling the switch
GETSIZE when invoking hsc. This will hsc tell to analyse
the image the attribute SRC refers to, and append the
attributes WIDTH and HEIGHT with the
dimensions obtained from the image data.
If you have already set those attributes yourself, hsc will only validate the values, and warn about mismatches.
Take a look at this nice picture of some nice guy:
<IMG SRC="image/niceguy.gif" ALT="Picture of some nice guy">but if a document called niceguy.hsc is converted using
hsc niceguy.hsc TO niceguy.html GETSIZEthe
<IMG>-tag seen above will be extended to
<IMG SRC="image/niceguy.gif" ALT="Picture of some nice guy" WIDTH="64" HEIGHT="64">in the html-object. If you do not like the double quotes assigned to the size values, use the CLI-option QUOTESTYLE to change this behavior.
In the early times of w3, this was the only format supported by most browsers. It features only indexed-color (16 or 256 colors) and an ugly looking progressive display option. It became very popular in a negative sense because of it's compression algorithm and the associated copyright.
Bye the way, did you know that "The Graphics Interchange Format(c) is the Copyright property of CompuServe Incorporated. GIF(sm) is a Service Mark property of CompuServe Incorporated."? So now you do; if it makes them happy...
Essentially this format does a good job as an idiot indicator. This
already starts with the name: jfif is short for JPEG File Interchange
Format (because it uses jpeg compression for image data). Nevertheless
jfif-pictures will have a file extension set to ``.jpg'' or
``.jpeg''.
The main feature about jpeg compression is that it is lossy, which means that the output image is not identical to the input image. Documents about software using jpeg compression usually claim that you can obtain good compression levels with no visible change. As long as you do not start to rotate or apply other complex image processing operations on pictures, this might even be true. Otherwise an ugly grid will appear soon.
Most important jfif is commonly used to encode images of more or less undressed people. To store as many such pictures as possible on as less space as possible, the compression rate is usually set to a high value. This makes these people look if they are suffered by leprosy or just a drawing by Egon Schiele.
Furthermore many people outside English speaking countries pronounce jpeg (``jay-peg'') as GPEG (``gee-peg''), even if they are normally capable of proper English pronunciation.
...an extensible file format for the lossless, portable, well-compressed storage of raster images. PNG provides a patent-free replacement for the GIF format and can also replace many common uses of TIFF format. Indexed-color, grayscale, and truecolor images are supported, plus an optional alpha channel. Sample depths range from 1 to 16 bits. PNG is designed to work well in online viewing applications, such as the World Wide Web, and so it is fully streamable with a progressive display option.
Above all PNG supports most obvious things several other formats failed to include. There is nothing really remarkable about it, but today one has the be glad even about this. So it can be said that PNG is one of the view positive things that happened in the last ten years.
But even despite that their is free source code available to read PNG-images, and the word ``Network'' is part of it's name (to conform to the hype), only few applications and w3-browsers support it for now.