Image Formats and Web design: JPG GIF PNG and SVG

The JPEG image format was developed by the Joint Photographic Experts Group in the early 90s. JPEG images most often end with the file extension. jpg; although. jpeg,. JPEG,. JPG,. jpg,. jpe,. jfif, and. jfi are also used. JPEG is a lossy bitmap compression algorithm meant primarily for digital photos. Lossy means that when JPEG images are saved they are compressed to less than their original size, but this comes with a loss in quality. Generally when saving a JPEG, compression is defined in percentages, with 100% being the highest quality but biggest file size. As a rough guide, 95% to 85% is good for logos and images used in formatting. Images of people or landscapes can go down to as low as 65% without obviously noticeable artifacts on the image.

For web designers JPEGs save space and load time, and offer a good general image format for digital photos and some logos. When using JPEGs you must be careful to avoid image degradation convert png to svgconvert png to svg. If a JPEG is edited and then saved again as a JPEG, your image will have deteriorated in quality because it has been compressed twice. Sometimes in only two or three generations this can render the image unusable. It is always best to save your images in a lossless format, such as. png,. tiff,. raw, or. xcf, and then, when needed, save the file as a JPEG. JPEGs are widely compatible on all modern browsers and are the most used image format on the web.

The GIF format, or Graphics Interchange Format, was introduced in 1987 by CompuServe and recognizable by the. gif file extension. It is a lossless bitmap compression format for color images and animation allowing the use of 256 colors out of a palette of 16 million. Lossless means that all of the information in the original image is saved in the saved GIF, although, because GIF only supports 256 colors it isn’t truly a perfect reproduction to the viewer.

Today, GIF is used to display things like buttons and low/med-quality animation on websites. GIF is not recommended for use with photographs due to the 256 color limitation, although there are workarounds. GIF animated buttons and the like were once popular, now they are fading from use, particularly due to Flash and better taste. Notably, GIF supports transparency, allowing the use of on or off “see-through” effects with images. Currently, PNG and MNG are in the process of superseding the GIF image format.

PNG is a bitmap image format with lossless image compression and uses the. png or. PNG file extension. PNG was developed as a license-free replacement to GIF, albeit without animation support. MNG, PNG’s cousin, was developed to succeed GIF animation feature. PNG has more advanced transparency options than GIF, allowing a full range of transparency as shown in the picture below. However, Internet explorer 6 does not support native alpha-channel transparency, however, in Windows Internet explorer 7 this is remedied. As of now PNG is less well supported than GIF by modern browsers.

SVG, or Scalable Vector Graphics, is one of the most interesting, and potentially useful image formats today. Unlike the other formats here, SVG is a XML mark-up language for vector graphics. Vector graphics, according to Wikipedia, is the use of geometrical primitives such as points, lines, curves, and polygons to represent images in computer graphics. Instead of having all of the information for each pixel in an image, as all of the prior image formats do, SVG defines things in these geometrical primitives. This means, when you increase the size of an SVG image, it always stays sharp, and never becomes pixilated. This can be quite useful for logos and other simple graphics, allowing for many different sizes of the same image to be used with no loss in quality. Also, SVG images typically have very small file sizes. As seen in the picture, SVG graphics are not photo-realistic. They also require different skills and, generally, different programs to create them. Body Mass Index (BMI for short) is a way of evaluating someone’s weight in relation to their height. The body Mass Index is sometimes referred to as the Quetelet’s index which is named after Belgian pioneer Lambert Adolphe Jacques Quetelet who made the system during the nineteenth century. A person’s obese level or obesity severity is determined primarily by their BMI using one of the BMI formulas (BMI formulae). BMI can also determine other weight levels such as underweight, normal weight and overweight. BMI does not measure a person’s actual body fat.

A prevalent formula used to calculate one’s BMI and obesity severity is in the International System of Units, commonly referred to as SI units or metric. This is someone’s weight in kilograms divided by their height in metres squared, shown as BMI = kg / m². The ” ² ” simply means that you’re multiplying the number prior to it twice. For example 1. 5m² would give you a figure of 2. 25 since its simply 1. 5 x 1. 5.

The first one based on imperial units is calculated by using one’s weight in pounds (lbs) multiplied by 703 (seven hundred and three) and then divided by their height in inches squared. This can be shown as BMI = (lbs x 703) / in². What’s in the parenthesis is what should be worked out first and then divided by inches squared. Another way people calculate this is BMI = (lbs / in²) and then multiplying what they get by 703.

The second one based on imperial units is calculated by using one’s weight in pounds (lbs) again but this time multiplied by 4. 88 (four decimal eight eight) then divided by their height in feet squared. This can be shown as BMI = (lbs x 4. 88) / ft². Another way people calculate this is BMI = (lbs / ft²) and multiplying what they get by 4. 88.

From any of the three BMI formulas mentioned above, if the end result is 30 or more, the person being tested is obese and has an obese level associated with their BMI. A BMI ranging from 25 to 29. 99 is classed as overweight. Under 18. 5 BMI is classed as underweight. The optimal BMI for individuals is from 18. 5 to 24. 99, that is where you should be.

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