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FROM: mkhanum@hotmail.com (Musthari Khanum)
DATE: May 16, 2000 TIME: 15:38:13 REMOTE IP: 64.20.15.149 |
Images on the Web :-) |
We all need images to express things better in our lives. Today our lives revolve around Computers. More and more individuals are getting familiar with using Computers, especially by using Internet. Websites use graphics to make things understandable for these individuals. Have you ever wondered how they get the graphics there? I know I have. Giant images posted in websites, that take forever to load, make me frustrated. Some times I get totally confused as to which image compression format to choose. In this article I am going to discuss about GIF, JPEG, and PNG image file formats and review their algorithms. I am also going to talk about how to get digital images on the web. This will help you understand more about Computer Graphics, and help you use graphics in your own website.
JPEG/JPG
The Joint Photo Experts Group (JPEG) format is primarily used to compress photo-realistic images very well. When the image is compressed, the quality of the image is actually lowered because JPEG uses a lossy-compression algorithm. In images with areas of solid color, such as a cartoon for example, some graininess can be observed around the edges of shapes. However in images with few solid areas of color, the artifacts and quality degradation is fairly well hidden. Also, JPEG wouldn't be a wise choice for images that are very small, such as thumbnails, where every pixel is important. This is because the compression may destroy these details. GIF, in these cases, would be more apparent choice.
GIF
The Compuserve GIF89 format has a lossless LZW compression algorithm, so image is usually not compressed nearly as much as JPEG, but when the image is compressed the quality is not lost. GIF89 has 2 other important features, aside from lossless compression. One feature is the ability of a GIF to contain animation, meaning that several images are stored in a single GIF, and then played back sequentially. Information like the delay between frames, or loop points, is also stored. The other feature is the ability of GIF to have a transparency color, and every pixel painted with that color becomes clear when viewed in the browser. So you can have parts of image show through to the background. Some of the downsides of GIF are that the transparency is either transparent, or not, and that it can only store 256 colors. There are no 50% transparencies, etc, and this usually results in problems when one tries to make an anti-aliased image transparent, because you end up getting little white/ black pixels around the edge. This is where PNG comes in.
PNG
Before it was used on the web, graphic designers storing high-quality photos or 3D renderings commonly used Portable Network Graphic(PNG). PNG is also commonly used to store digital animation frames before transfer to VHS or Film. PNG, like GIF, uses LZW lossless compression, so the image is not damaged or modified when compressed. Also, PNG has a full 256 color alpha channel, allowing 256 different levels of transparency, from completely clear to fully opaque. PNG also stores gamma information (display brightness calibration). Another PNG's features is its ability to allow the user to choose between 256 color and 16.7M color modes, so one can save some filesize if they do not need the full gamut of colors. PNG also supports interlacing, where the image comes on the screen blurry at first, and then becomes progressively clearer as the image is downloaded. Currently, PNG is supported on both MSIE and Netscape 4.0, with browser support growing fast.
How to get digital images? 1)Kodak PCD 2)Slide Scanner 3)Framegrabber 4)Digital Camera 5)Scanner Different ways of acquiring images are listed above. The PCD proved to be an inexpensive method to archive images. Neither colors nor details will change over the life span of the disc, which is currently assumed to be longer than thirty years. The images on a Photo Compact Disk proved superior to the ones that were scanned via the slide scanner with respect to resolution, brightness, and color accuracy. Using video together with a frame grabber card with limited resolution, proved insufficient because colors do not correspond well.
Pictures are definitely an important source to attract people to your website. After all this information I hope you got the beginning information you needed. If you have any questions feel free to ask.
Question: During my research, there were few options for Images on the Web. When I tried to open them, there were pictures that I didn’t wanted to see. Do you guys think that there should be some sort of Warning before those ‘R’ rated pictures opened up?
However, most graphics software packages (Photoshop, etc) does pay royalties to Unisys, so all GIFs created from those apps would be legal. PNG as far as I know does not use LZW compression but what it calles wavelet compression. PNGs can be both lossless or lossy, and you can combine loseless and lossy compression to different areas of the same image. Just make up your choice.
REPLY TO THIS ARTICLE
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Re: Images on the Web :-)
Posted by Bougataya Mehdi on May 30, 2000 at 12:02:38 at IP 172.147.168.64
I think that those R pictures should be stopped from being exposed on the internet. But in fact reaserchs are going on led by AI experts, and those reseach are about a software which should scan any picture and if the skin exposure is in certain percentage the image is rejected. Re: Images on the Web :-)
Posted by Bobbie Razo on May 28, 2000 at 18:31:27 at IP 216.192.103.36
I think there should definitely some kind of warning before being displayed with R rated pictures. But somehow, no matter what kind of censorship is done, those things always filter through. An example is by having an account with hotmail where you get soo much junk mails like those! Re: Images on the Web :-)
Posted by HOI CHUN YUNG on May 27, 2000 at 1:20:50 at IP 209.255.49.55
PNG, is especially design for Web, small file with JPG quality. But be carefully, to use those it, some company will hide the cookie file in the single pixel GIF and any image file, virus will be brought by this way. Re: Images on the Web :-)
Posted by Jick Gee Chui on May 24, 2000 at 12:13:56 at IP 163.238.34.221
The Web image is a really fun stuff. You can share someone picture to make a thing to yourself.(e.g. Card, your Web page, etc.....)
But talk about virus; of couse it must be careful to choose a good reputation site... Anyway after you online, it must has some risk. Just Becareful. Re: Images on the Web :-)
Posted by Joseph Fardella on May 23, 2000 at 23:36:38 at IP 63.23.128.165
Some type of monitoring is necessary for information on the net. This should not be seen as censorship, but as categorization. People should not be inadvertantly exposed to images they do not wish to see. The only problem with this is enforcing it, this is the hardest part of such an implementation. Re: Images on the Web :-)
Posted by Kam Tsui on May 23, 2000 at 22:54:38 at IP 4.54.120.229
Image is not like text, which can tell it is an adult article by finding some of the "words". How can we know if it is one of "those" images? by certain color? or by what? nothing at all. Therefore i think it is unpreventable to see "those" images. Re: Images on the Web :-)
Posted by Dennis Healy on May 23, 2000 at 0:44:25 at IP 152.163.194.207
I think that an image filter or stamp is a great idea. Friends of mine have children who use the web for school and the scope of their access is very limited for fear they may open some eye-poping pics. They constantly want more access and are disapointed when they cannot go to sites they know are ok but are suspect and not available to them. Re: Images on the Web :-)
Posted by mkhanum@hotmail.com on May 22, 2000 at 17:34:50 at IP 163.238.9.13
I didn't download any picutes, it just came automatically on the screen. That's why I think it's wrong and there should be something done about it. Re: Images on the Web :-)
Posted by Han on May 18, 2000 at 14:41:07 at IP 198.83.28.35
FOr those who don't know... UNISYS, who owns the patent for LZW compression, is cracking down on sites that did not pay for use of the LZW patent. That means sites that uses GIF images created by software that does not pay royalties to Unisys, can be forced by law to pay a $5000 site fee. Of course, companies can fight this with Unisys in court, but it is not worth it for $5000. Re: Images on the Web :-)
Posted by kit Woo on May 18, 2000 at 2:41:26 at IP 152.172.131.138
I do agree with Jumoke Atobatele. You should expect to see any kind of picture when you download from an unknown image. Same for email, you should expect to receive a virus infection from opening an unknown email. ("ILOVEYOU" BUGS) Re: Images on the Web :-)
Posted by Jumoke Atobatele on May 17, 2000 at 17:29:57 at IP 163.238.34.222
Definately, I think it is left to the viewer to think twice before downloading any image. Thinking of all the past experiences with virus, down-loading any image would definately be at the user risk be it adult or not. And even if controls are being set considering these images, I could say that would not totally eliminate this problem. Best advise is to think twice when on the net.
