Just Say Hi 2 Net User

Since time immemorial, I just can't recalled when was the last time I chatted with someone using mIRC. At that time, I was looking for an online dating especially someone whose passive like me. I grew up as a native teenager who seek for alternative loves and passion.

Until then, I wandered and started digging for the true meaning of love. I realised if I want to live happily ever after (like a fantasy maybe), I need to find my dates, through which I found many online dating website that offered these services.

Online dating website truely can look after someone suitable for your life. But please beware of someone who poised to be the true love of your life. It can be harmful enough if someone camouflaged and doomed you. That is what we called as blind date :)

So, in my opinion go for an online dating website that can offered you many choices of recognition as love is around you!!

What are good "quality" settings for JPEG?

Most JPEG compressors let you pick a file size vs. image quality tradeoff by selecting a quality setting. There seems to be widespread confusion about the meaning of these settings. "Quality 95" does NOT mean "keep 95% of the information", as some have claimed. The quality scale is purely arbitrary; it's not a percentage of anything.

In fact, quality scales aren't even standardized across JPEG programs. The quality settings discussed in this article apply to the free IJG JPEG software, and to many programs based on it. Some other JPEG implementations use completely different quality scales.

For example:
* Apple used to use a scale running from 0 to 4, not 0 to 100.
* Recent Apple software uses an 0-100 scale that has nothing to do with the IJG scale (their Q 50 is about the same as Q 80 on the IJG scale).
* Paint Shop Pro's scale is the exact opposite of the IJG scale, PSP setting N = IJG 100-N; thus lower numbers are higher quality in PSP.
* Adobe Photoshop doesn't use a numeric scale at all, it just gives you "high"/"medium"/"low" choices. (But I hear this is changing in 4.0.)

Fortunately, this confusion doesn't prevent different implementations from exchanging JPEG files. But you do need to keep in mind that quality scales vary considerably from one JPEG-creating program to another, and that just saying "I saved this at Q 75" doesn't mean a thing if you don't say which program you used.

In most cases the user's goal is to pick the lowest quality setting, or smallest file size, that decompresses into an image indistinguishable from the original. This setting will vary from one image to another and from one observer to another, but here are some rules of thumb.

For good-quality, full-color source images, the default IJG quality setting (Q 75) is very often the best choice. This setting is about the lowest you can go without expecting to see defects in a typical image. Try Q 75 first; if you see defects, then go up.

If the image was less than perfect quality to begin with, you might be able to drop down to Q 50 without objectionable degradation. On the other hand, you might need to go to a *higher* quality setting to avoid further loss. This is often necessary if the image contains dithering or moire patterns.

Except for experimental purposes, never go above about Q 95; using Q 100 will produce a file two or three times as large as Q 95, but of hardly any better quality. Q 100 is a mathematical limit rather than a useful setting. If you see a file made with Q 100, it's a pretty sure sign that the maker didn't know what he/she was doing.

If you want a very small file (say for preview or indexing purposes) and are prepared to tolerate large defects, a Q setting in the range of 5 to 10 is about right. Q 2 or so may be amusing as "op art". (It's worth mentioning that the current IJG software is not optimized for such low quality factors. Future versions may achieve better image quality for the same file size at low quality settings.)

If your image contains sharp colored edges, you may notice slight fuzziness or jagginess around such edges no matter how high you make the quality setting. This can be suppressed, at a price in file size, by turning off chroma downsampling in the compressor. The IJG encoder regards downsampling as a separate option which you can turn on or off independently of the Q setting. With the "cjpeg" program, the command line switch "-sample 1x1" turns off downsampling; other programs based on the IJG library may have checkboxes or other controls for downsampling. Other JPEG implementations may or may not provide user control of downsampling. Adobe Photoshop, for example, automatically switches off downsampling at its higher quality settings. On most photographic images, we recommend leaving downsampling
on, because it saves a significant amount of space at little or no visual penalty.

For images being used on the World Wide Web, it's often a good idea to give up a small amount of image quality in order to reduce download time. Quality settings around 50 are often perfectly acceptable on the Web. In fact, a user viewing such an image on a browser with a 256-color display is unlikely to be able to see any difference from a higher quality setting, because the browser's color quantization artifacts will swamp any imperfections in the JPEG image itself. It's also worth knowing that current progressive-JPEG-making programs use default progression sequences that are tuned for quality settings around 50-75: much below 50, the early scans will look really bad, while much above 75, the later scans won't contribute anything noticeable to the picture.

How well does JPEG compress images?

Very well indeed, when working with its intended type of image (photographs and suchlike). For full-color images, the uncompressed data is normally 24 bits/pixel. The best known lossless compression methods can compress such data about 2:1 on average. JPEG can typically achieve 10:1 to 20:1 compression without visible loss, bringing the effective storage requirement down to 1 to 2 bits/pixel. 30:1 to 50:1 compression is possible with small to moderate defects, while for very-low-quality purposes such as previews or archive indexes, 100:1 compression is quite feasible. An image compressed 100:1 with JPEG takes up the same space as a full-color one-tenth-scale thumbnail image, yet it retains much more detail than such a thumbnail.

For comparison, a GIF version of the same image would start out by sacrificing most of the color information to reduce the image to 256 colors (8 bits/pixel). This provides 3:1 compression. GIF has additional "LZW" compression built in, but LZW doesn't work very well on typical photographic data; at most you may get 5:1 compression overall, and it's not at all uncommon for LZW to be a net loss (i.e., less than 3:1 overall compression). LZW *does* work well on simpler images such as line drawings, which is why GIF handles that sort of image so well. When a JPEG file is made from full-color photographic data, using a quality setting just high enough to prevent visible loss, the JPEG will typically be a factor of four or five smaller than a GIF file made from the same data.

Gray-scale images do not compress by such large factors. Because the human eye is much more sensitive to brightness variations than to hue variations, JPEG can compress hue data more heavily than brightness (gray-scale) data. A gray-scale JPEG file is generally only about 10%-25% smaller than a full-color JPEG file of similar visual quality. But the uncompressed gray-scale data is only 8 bits/pixel, or one-third the size of the color data, so the calculated compression ratio is much lower. The threshold of visible loss is often around 5:1 compression for gray-scale images.

The exact threshold at which errors become visible depends on your viewing conditions. The smaller an individual pixel, the harder it is to see an error; so errors are more visible on a computer screen (at 70 or so dots/inch) than on a high-quality color printout (300 or more dots/inch). Thus a higher-resolution image can tolerate more compression ... which is fortunate considering it's much bigger to start with. The compression ratios quoted above are typical for screen viewing. Also note that the threshold of visible error varies considerably across images.

When should I use JPEG, and when should I stick with GIF?

JPEG is *not* going to displace GIF entirely; for some types of images, GIF is superior in image quality, file size, or both. One of the first things to learn about JPEG is which kinds of images to apply it to.

Generally speaking, JPEG is superior to GIF for storing full-color or gray-scale images of "realistic" scenes; that means scanned photographs, continuous-tone artwork, and similar material. Any smooth variation in color, such as occurs in highlighted or shaded areas, will be represented more faithfully and in less space by JPEG than by GIF.

GIF does significantly better on images with only a few distinct colors, such as line drawings and simple cartoons. Not only is GIF lossless for such images, but it often compresses them more than JPEG can. For example, large areas of pixels that are all *exactly* the same color are compressed very efficiently indeed by GIF. JPEG can't squeeze such data as much as GIF does without introducing visible defects. (One implication of this is that large single-color borders are quite cheap in GIF files, while they are best avoided in JPEG files.)

Computer-drawn images, such as ray-traced scenes, usually fall between photographs and cartoons in terms of complexity. The more complex and subtly rendered the image, the more likely that JPEG will do well on it. The same goes for semi-realistic artwork (fantasy drawings and such). But icons that use only a few colors are handled better by GIF.

JPEG has a hard time with very sharp edges: a row of pure-black pixels adjacent to a row of pure-white pixels, for example. Sharp edges tend to come out blurred unless you use a very high quality setting. Edges this sharp are rare in scanned photographs, but are fairly common in GIF files: consider borders, overlaid text, etc. The blurriness is particularly objectionable with text that's only a few pixels high. If you have a GIF with a lot of small-size overlaid text, don't JPEG it. (If you want to attach descriptive text to a JPEG image, put it in as a comment rather than trying to overlay it on the image. Most recent JPEG software can deal with textual comments in a JPEG file, although older viewers may just ignore the comments.)

Plain black-and-white (two level) images should never be converted to JPEG; they violate all of the conditions given above. You need at least about 16 gray levels before JPEG is useful for gray-scale images. It should also be noted that GIF is lossless for gray-scale images of up to 256 levels, while JPEG is not.

If you have a large library of GIF images, you may want to save space by converting the GIFs to JPEG. This is trickier than it may seem --- even when the GIFs contain photographic images, they are actually very poor source material for JPEG, because the images have been color-reduced. Non-photographic images should generally be left in GIF form. Good-quality photographic GIFs can often be converted with no visible quality loss, but only if you know what you are doing and you take the time to work on each image individually. Otherwise you're likely to lose a lot of image quality or waste a lot of disk space ... quite possibly both.

Why use JPEG?

There are two good reasons: to make your image files smaller, and to store 24-bit-per-pixel color data instead of 8-bit-per-pixel data.

Making image files smaller is a win for transmitting files across networks and for archiving libraries of images. Being able to compress a 2 Mbyte full-color file down to, say, 100 Kbytes makes a big difference in disk space and transmission time! And JPEG can easily provide 20:1 compression of full-color data. If you are comparing GIF and JPEG, the size ratio is usually more like 4:1.

Now, it takes longer to decode and view a JPEG image than to view an image of a simpler format such as GIF. Thus using JPEG is essentially a time/space tradeoff: you give up some time in order to store or transmit an image more cheaply. But it's worth noting that when network transmission is involved, the time savings from transferring a shorter file can be greater than the time needed to decompress the file.

The second fundamental advantage of JPEG is that it stores full color information: 24 bits/pixel (16 million colors). GIF, the other image format widely used on the net, can only store 8 bits/pixel (256 or fewer colors). GIF is reasonably well matched to inexpensive computer displays --- most run-of-the-mill PCs can't display more than 256 distinct colors at once. But full-color hardware is getting cheaper all the time, and JPEG photos look *much* better than GIFs on such hardware. Within a couple of years, GIF will probably seem as obsolete as black-and-white MacPaint format does today. Furthermore, JPEG is far more useful than GIF for exchanging images among people with widely varying display hardware, because it avoids prejudging how many colors to use. Hence JPEG is considerably more appropriate than GIF for use as a Usenet and World Wide Web standard photo format.

A lot of people are scared off by the term "lossy compression". But when it comes to representing real-world scenes, *no* digital image format can retain all the information that impinges on your eyeball. By comparison with the real-world scene, JPEG loses far less information than GIF. The real disadvantage of lossy compression is that if you repeatedly compress and decompress an image, you lose a little more quality each time. This is a serious objection for some applications but matters not at all for many others.

What is JPEG?

JPEG (pronounced "jay-peg") is a standardized image compression mechanism. JPEG stands for Joint Photographic Experts Group, the original name of the committee that wrote the standard.

JPEG is designed for compressing either full-color or gray-scale images of natural, real-world scenes. It works well on photographs, naturalistic artwork, and similar material; not so well on lettering, simple cartoons, or line drawings. JPEG handles only still images, but there is a related standard called MPEG for motion pictures.

JPEG is "lossy," meaning that the decompressed image isn't quite the same as the one you started with. (There are lossless image compression algorithms, but JPEG achieves much greater compression than is possible with lossless methods.) JPEG is designed to exploit known limitations of the human eye, notably the fact that small color changes are perceived less accurately than small changes in brightness. Thus, JPEG is intended for compressing images that will be looked at by humans. If you plan to machine-analyze your images, the small errors introduced by JPEG may be a problem for you, even if they are invisible to the eye.

A useful property of JPEG is that the degree of lossiness can be varied by adjusting compression parameters. This means that the image maker can trade off file size against output image quality. You can make *extremely* small files if you don't mind poor quality; this is useful for applications such as indexing image archives. Conversely, if you aren't happy with the output quality at the default compression setting, you can jack up the quality until you are satisfied, and accept lesser compression.

Another important aspect of JPEG is that decoders can trade off decoding speed against image quality, by using fast but inaccurate approximations to the required calculations. Some viewers obtain remarkable speedups in this way. (Encoders can also trade accuracy for speed, but there's usually less reason to make such a sacrifice when writing a file.)