A digital image is composed of a finite numberof elements called pixels, each of which has a particular location and value(intensity). Typically, pixels are organized in an ordered 2-dimentional array(Matrix). The size of an image isdetermined by the dimensions of this pixel array. The image width and height are the number ofcolumns and the number of rows in the array respectively. Thus, the pixel array is a matrix of M columnsx N rows. To refer to a specific pixelwithin the image matrix, we define its coordinate at x and y positions.Each pixel hasits own intensity value, or brightness.
If all the pixels have the same value, the image will be a uniform shadei.e. all black, white, gray, or some other shade. It is in the type of intensity used for eachpixel that image types vary from one another.
Black and white images only have intensity of the black and white. Grayscaleimages have intensity from the darkest gray (black) to lightest gray (white).Color images, on the other hand, have intensity from the darkest and lightestof three different colors, Red, Green, and Blue. The various mixtures of these colorintensities produce a color image.Intensityvalues in digital images are defined by bits. A bit is binary and only has two possible values, 0 or 1. An 8-bit intensity range has 256 possiblevalues, 0 to 255.
Two most basictypes of digital images are:Black &White Grayscale Red-Green-Blue. Types ofDigital Image FilesTIFF (also known as TIF), file types ending in .tifTIFF standsfor Tagged Image File Format. TIFF images create very large file sizes. TIFFimages are uncompressed and thus contain a lot of detailed image data. TIFFsare also extremely flexible in terms of color and content.JPEG (also known as JPG), file types ending in .
jpgJPEG standsfor Joint Photographic Experts Group, which created this standard for this typeof image formatting. JPEG files are images that have been compressed to store alot of information in a small-size file. Most digital cameras store photos inJPEG format, because then you can take more photos on one camera card than youcan with other formats.GIF, file types ending in .gifGIF stands forGraphic Interchange Format. This format compresses images but, as differentfrom JPEG, the compression is lossless (no detail is lost in the compression,but the file can’t be made as small as a JPEG).
PNG, file types ending in .pngPNG stands forPortable Network Graphics. It was created as an open format to replace GIF,because the patent for GIF was owned by one company and nobody else wanted topay licensing fees. It also allows for a full range of colour and bettercompression.Raw image filesRaw imagefiles contain data from a digital camera (usually).
The files are called rawbecause they haven’t been processed and therefore can’t be edited or printedyet. There are a lot of different raw formats–each camera company often has itsown proprietary format.
