Image File Formats - how do they compare?

Question

Image File Formats - how do they compare?

Answer 1

Ok a BMP is basically an uncompressed image file so you see the image exactly as it was made but this results in large files.



A GIF is for simple images and animation but is restricted to 256 colours.



PNG is set to replace IF as it supports more colours but makes slightly larger files.



JPG is used for photographs and compressed them to make them smaller. This is why sometimes in photos you see weird blocks when the image is compressed a lot.



TIFF I beleive is an uncompressed image file.



RAW is used by a few cameras and is the image exactly as the camera saw it.

Answer 2

JPEG - right for photo images, ideally small e.g. the ones used on a website, small files or for email.

TIFF - used commonly for archiving important images, proefessional standard (most widely supported format across all OS), no quality loss due to compression as compared to JPEG's.

PNG - incorporates special preprocessing filters (best for archival storage when appearance is important)

GIF - good for graphics and logos

Answer 3

jpeg is the most common, so loads of free graphics programmes work with it, the file sizes are relatively small as well, but at a cost of compressing and losing some quality. The professionals use RAW but the file sizes can be immense.

Answer 4

Images are made up of many pixels (dots that make up the image). For a basic image, lets say one of 640 x 480 pixels, there are 307'200 pixels in the image.



For each pixel in the image 32 bits of data are required to describe the colour of that pixel.



307'200 x 32 = 9'830'400



So that means 9'830'400 bits are required to describe an image of with size 640 x 480 pixels.





TIFF images are your basic raw image format, so it uses the method described above to store the images. It means that the bigger the image, the more information that is required to describe it and it's pixels. TIFF format is a high quality format that stores the image exactly as it is in the original image.



http://en.wikipedia.org/wiki/TIFF



As you can imagine, as the dimensions of the image get bigger the more information is required to describe that image.



In the mid 80's, a commitee was formed to think of ways to reduce the amount of information needed to describe an image.



The commitee was called the Joint Photographic Experts Group (JPEG). They came up with a new image format named JPEG that could store the same image as a TIFF but using less data.



http://en.wikipedia.org/wiki/JPEG



They developed a mathematical formula called a Discrete Cosine Transform (DCT) that could analyse the image and that could decide which parts of the image were important and which parts the viewer would not be able to notice if they were changed slightly.



When saving an image in JPEG format, the computer stores information about the detailed areas but it encodes less detailed areas using a special algorithm. This changes the image quality slightly but reduces the filesize immensly.



The more quality loss, the more reduction in filesize that can be achieved. This is why JPEG is known as a 'lossy' file format.



Around the same time, Compuserve, an Internet Service Provider were experimenting with ways to store images for graphics. They came up with GIF (Graphics Interchange Format) to save there images. The GIF format also uses a mathematical formula to save it's images, but the formula it uses only supports 256 colours, this means that images saved in GIF format can only be made of up of 256 unique colours.



http://en.wikipedia.org/wiki/Graphics_Interchange_Format





The PNG (Portable Network Graphics) is the next generation of the GIF format. It supports up to 16.7 million colours but it is based upon the same mathematical formula as the GIF format to reduce the filesize.



http://en.wikipedia.org/wiki/Portable_Network_Graphics









Summary:



TIFF

Raw images with no processing or compression. What you see is what you get. Very big filesize.



JPEG

Good for photographs, compresses images anywhere between 10:1 to 50:1 depending upon how much quality loss is acceptable to the viewer.



GIF

Good for graphics such as logos, buttons, icons, etc. Only supports 256 colours but can compress images to a smaller size.



PNG

Good for graphics, supports 16.7 millions colours and is the next generation for graphics images. Can be used for photographs but still not as good as JPEG.









I hope I've fully answered your question. Please rate my answer if you find it useful.

Answer 5

Peice of cake, Rockstar......



PDF = Portable Data File or Postscript Data Format is the most versitalle file format there is for images so try and always use that or an EPS file (Encapselated Postscript File)........ JPG is the most common image file and the widest used format in the world so that's why you see it all the time....... PNG is a little higher quality standard that JPG....... TIFF would be the highest quality for standard image files (Note: PDF and EPS are not standard image files, they are graphic design standard image files...... there's a big difference there)....... GIF and BMP are the very lowest image files mainly used for website so there will be a low loading time, that is their main purpose...... also note that GIF is the only file format that can keep a transparent background when working with graphic designs..... hope this helped a little...... there is a huge amount of differences between all the differnt formats.

Answer 6

its all about the size, compression rate and quality of the images

Answer 7

JPEG (Joint Photographic Experts Group) files are a lossy format (in most cases). The DOS filename extension is JPG, although other operating systems may use JPEG. Nearly all digital cameras have the option to save images in JPEG format. The JPEG format supports 8 bits per color – red, green, and blue, for 24-bit total – and produces relatively small file sizes. The compression when not too severe does not detract noticeably from the image. But JPEG files can suffer generational degradation when repeatedly edited and saved. Photographic images may be better stored in a lossless non-JPEG format if they will be re-edited in future, or if the presence of small "artifacts" (blemishes), due to the nature of the JPEG compression algorithm, is unacceptable. JPEG is also used as the image compression algorithm in many Adobe PDF files.



PNG (Portable Network Graphics) file format is regarded, and was made as, the free and open-source successor to the GIF file format. The PNG file format supports true color (16 million colors) whereas the GIF file format only allows 256 colors. PNG excels when the image has large areas of uniform color. The lossless PNG format is best suited for editing pictures, and the lossy formats like JPG are best for final distribution of photographic-type images because of smaller file size. Many older browsers do not yet support the PNG file format, however with the release of Internet Explorer 7 all popular modern browsers fully support PNG. The Adam7-interlacing allows an early preview even when only a small percentage of the data of the image has been transmitted.



GIF (Graphic Interchange Format) is limited to an 8-bit palette, or 256 colors. This makes the GIF format suitable for storing graphics with relatively few colors such as simple diagrams, shapes, logos and cartoon style images. The GIF format supports animation and is still widely used to provide image animation effects. It also uses a lossless compression that is more effective when large areas have a single color, and ineffective for detailed images or dithered images.



TIFF (Tagged Image File Format) is a flexible image format that normally saves 8 or 16 bits per color – red, green and blue – for a total of 24 or 48 bits, and uses a filename extension of TIFF or TIF. TIFF's flexibility is both a feature and a curse, with no single reader capable of handling all the different varieties of TIFF files. TIFF can be lossy or lossless. Some types of TIFF files offer relatively good lossless compression for bi-level (black and white, no grey) images. Some high-end digital cameras have the option to save images in the TIFF format, using the LZW compression algorithm for lossless storage. The TIFF image format is not widely supported by web browsers. TIFF is still widely accepted as a photograph file standard in the printing industry. TIFF is capable of handling device-specific color spaces, such as the CMYK defined by a particular set of printing press inks.



Basically JPG for High-Quality compressed files for the web or elsewhere. GIF for lower quality, transparent and animated graphics. PNG can also do transparencies...