Image

There are two kinds of computer graphics - raster (composed of pixels) and vector (composed of paths). Raster images are more commonly called bitmap images. A bitmap image uses a grid of individual pixels where each pixel can be a different color or shade. Bitmaps are composed of pixels. Vector graphics use mathematical relationships between points and the paths connecting them to describe an image. Vector graphics are composed of paths.

Images may be two-dimensional, such as a photograph, screen display, and as well as a three-dimensional, such as a statue or hologram. They may be captured by optical devices—such as cameras, mirrors, lenses, telescopes, microscopes, etc. and natural objects and phenomena, such as the human eye or water surfaces.

A digital image is a numeric representation (normally binary) of a two-dimensional image.

Image file formats are standardized means of organizing and storing digital images. Image files are composed of either pixels, vector (geometric) data, or a combination of the two. Whatever the format, the files are rasterized to pixels when displayed on most graphic displays. The pixels that constitute an image are ordered as a grid (columns and rows); each pixel consists of numbers representing magnitudes of brightness and color.

Image formats:

 BMP Bitmap: This was probably the first type of digital image format. Every picture on a computer seemed to be a BMP. BMP files are uncompressed, hence they are large; the advantage is their simplicity and wide acceptance in Windows programs.

 JPG, JPEG JPEG (Joint Photographic Experts Group) is a compression method; JPEG-compressed images are usually stored in the JFIF (JPEG File Interchange Format) file format. JPEG compression is (in most cases) lossy compression. The JPEG/JFIF filename extension is JPG or JPEG. Nearly every digital camera can save images in the JPEG/JFIF format, which supports 8 bits per color (red, green, blue) for a 24-bit total (16,777,216 color variations), producing relatively small files with a good quality.

 GIF (Graphics Interchange Format) Gif format is best used for text, line drawings, screen shots, cartoons, and animations. Gif is limited to a total number of 256 colors or less which supports for (red, green, blue) a 8-bit total. It is commonly used for fast loading web pages. It also makes a great banner or logo for your webpage. Animated pictures are also saved in GIF format. For example, a flashing banner would be saved as a Gif file. GIF supports Alpha Channel.

 PNG (Portable Networks Graphic) Apparently this is one of the best image formats; however it was not always compatible with all web browsers or image software. The PNG file format supports truecolor (16 million colors) while the GIF supports only 256 colors. PNG supports Alpha Channel.

 TIFF ( Tagged Image File Format) This file format stores files with virtually no compression and therefore is good for storing images that need to be edited and re-saved without suffering a compression loss. This file is commonly used for scanning, faxing, word processing, and so on. TIFF supports Alpha Channel.

Adobe Photoshop

Adobe Photoshop is a graphics editing program developed and published by Adobe Systems Incorporated. In 1987, Thomas Knoll, a PhD student at the University of Michigan began writing a program on his Macintosh Plus to display grayscale images on a monochrome display. This program, called Display, caught the attention of his brother John Knoll, an Industrial Light & Magic employee, who recommended Thomas turn it into a fully-fledged image editing program. Thomas took a six month break from his studies in 1988 to collaborate with his brother on the program, which had been renamed ImagePro. Later that year, Thomas renamed his program Photoshop

Tutorials:

1- Introduction to Adobe Photoshop part (1) 2- Introduction to Adobe Photoshop part (2)