Introduction to digital image editing

Digital image editing is done with computer programs called image editors to manipulate, enhance, and transform images. Special software programs called Vector graphics editor or Bitmap graphics editor perform these operations. These editors are capable of editing images in many diverse ways. Digital imaging is closely associated with digital photography and is used extensively in the fields of science, medicine, and forensics. This article is limited digital image editing associated with digital cameras and with digital photography. Image of the Wikimedia Commons logo. ... A vector graphics editor is a computer program that allows users to compose and edit vector graphics images interactively on the computer screen (compare with MetaPost) and save them in one of many popular vector graphics formats such as CDR, PDF, WMF or SVG. // Vector editors versus bitmap editors Vector... A bitmap graphics editor is a computer program that allows users to paint and edit pictures interactively on the computer screen and save them in one of many popular bitmap or raster formats such as JPEG, PNG, GIF and TIFF. Usually an image viewer is preferred over a bitmap graphics... A digital image is a representation of a two-dimensional image as a finite set of digital values, called picture elements or pixels. ... A SiPix digital camera next to a matchbox to show scale. ... The Nikon Coolpix 950 The Nikon Coolpix 3200 compact camera Digital photography, as opposed to film photography, uses an electronic sensor to record the image as a piece of electronic data rather than as chemical changes on film. ...

Basics of image editing

Images are stored in the computer in the form of a grid of picture elements called pixels. These pixels contain the image's color and brightness informatiion. Image editors can change the pixels to enhance the image in many ways. The pixels can be changed as a group, or individually, by the sophisticated algorithms within the image editors. A pixel (a contraction of picture element) is one of the many tiny dots that make up the representation of a picture in a computers memory. ... Flowcharts are often used to represent algorithms. ...

Image editing programs

Because of the popularity of digital cameras, image editing programs are readily available. Minimal programs, that do such operations as rotating and cropping (image)s are often provided within the digital camera itself, others are returned to the user on a compact disk (CD) when images are processed at a discount store. The more powerful programs contain algorithms that perform a large variety of advanced image manipulations. Popular digital image editors include Paint Shop Pro and Adobe Photoshop 2. ... A SiPix digital camera next to a matchbox to show scale. ... CD redirects here; see Cd for other meanings of CD. Image of a compact disc (pencil included for scale) A compact disc (or CD) is an optical disc used to store digital data, originally developed for storing digital audio. ... Paint Shop Pro (PSP) is a bitmap graphics editor for computers running the Microsoft Windows operating system that was originally published by Minneapolis-based Jasc Software. ... Adobe Photoshop is a graphics editor (with some text and vector graphics capabilities) developed and published by Adobe Systems. ...

Digital data compression

Image files need data compression to reduce file size and save storage space. Digital compression of images may take place in the camera, or can be done in the computer with the image editor. When images are stored in JPEG format, compression has already taken place. Both cameras and computer programs allow the user to set the level of compression. Some compression algorithms are lossless, notably PNG, which means no image quality is lost when the file is saved. The JPEG compression algorithm uses a lossy format, but the algorithm takes advantage of "psycho visual modeling" to reduce detail. The greater the compression, the less the quality. The JPEG algorithm utilizes the way the brain and eyes work to make loss of detail less noticeable. In computer science, data compression or source coding is the process of encoding information using fewer bits (or other information-bearing units) than a more obvious representation would use, through use of specific encoding schemes. ... A photo of a flower compressed with successively higher compression ratios from left to right. ... Lossless data compression is a class of data compression algorithms that allow the original data to be reconstructed exactly from the compressed data. ... PNG (Portable Network Graphics) is a lossless bitmap image format. ... A photo of a flower compressed with successively higher compression ratios from left to right. ... A lossy data compression method is one where compressing a file and then decompressing it retrieves a file that may well be different to the original, but is close enough to be useful in some way. ...

Image editor features

Listed below are some of the most used capabilities of the better image editors. The list is by no means all inclusive. There are a myriad of choices associated with the application of most of these features. Image of the Wikimedia Commons logo. ...

Image size change

Image editors can resize an image, making it larger, or smaller. High image resolution cameras can produce large images which are often reduced in size for Internet use.. Image editor programs use a mathematical process called re-sampling to calculate new pixel values whose spacing is larger or smaller than the original pixel values. Images for Internet use are kept small, say 640 x 480 pixels. The image resolution is a term that says something about how much image detail an image can hold. ...

Cropping an image

Digital editors are used to crop images. Cropping creates a new image by removing a desired rectangular portion from the image being cropped. The unwanted part of the image is discarded. Image cropping does not reduce the resolution of the area cropped. Best results are obtained when the original image has a high resolution. A primary reason for cropping is to improve the image composition in the new image.

Uncropped image from camera

Lilly cropped from larger image

Histogram uses

Image editors have provisions to create a image histogram of the image being edited. The histogram displays the brightness value of each pixel in the image along a 0 -255 baseline. Algorithms in the digital editor allow the user to visually adjust the brightness value of each pixel and to dynamically display the results as adjustments are made. Improvements in picture brightness and contrast can thus be obtained. In computer graphics, a color histogram is a representation of an image derived by counting the color of each pixel. ...

Cropped image of sunflower

Histogram of Sunflower image

Noise removal

Image editors have an algorithm which can add or remove noise an image. JPEG artifacts can be removed; scratches can re removed and an image can be despeckeled. Noise tends to invade images when pictures are taken in low light settings. A new picture can be antiqued by adding uniform monochrome noise. A thorough discussion of camera noise can be found at:Explanation of noise

Image orientation

Image editors have algorithms to all the image to rotated in any direction and to any degree. Mirror image can be created and images can be flipped (turned upside down. Images that ae out of line can be straightened and perspective can be adjusted.

Merging of images

Image editors have provisions for merging one or more individual images into a single image. The orientation and placement of each image can be controlled. The two images shown here were once individual studio portraits.

John and Bertha Phillips - 1910

Special effects

Image editors usually have a list of special effects that can create unusual results. Images to be skewed and distorted in various ways. Scores of special effects can be applied to an image which include various forms of distortion, artistic effects, geometric, and texture effects, and combinations thereof.

Change color depth

Image editors have provisions to change the color depth of images. Common color depths are 2, 16, 256, and 16million. The JPEG and PNG image format will store 16 million colors. There are also algorithms for grayscale. In computing, a grayscale or greyscale digital image is an image in which the value of each pixel is a single sample. ...

Lens correction

Image editors have provisions to correct images for various pincushion, fisheye, and barrel distortion. The corrections are subtle, but can improve the appearance of some images.

Contrast change and brightening

Image editors have provisions to change the contrast of images and brighten or darken the image. Many an underexposed image can be improved by using this feature.

Sharpening and softening images

Image editors have provisions to sharpen images, blur images, and to soften images. Portraits often appear more pleasing when softened. Red-eye, which occurs when flash photos are taken, can also be eliminated.

Color adjustments

Image editors have provisions to adjust the color of images in a variety of ways. The color balance can be improved, colors and be faded in and out, tones can be changes. Special effects, like sepia and grayscale can be added to an image.

Conclusion

Image editors provide the means for altering and improving images in an almost endless number of ways. They accept images in a large variety of image formats, and after changes are made they allow the changed image to be saved in any number of image formats, at almost any size, and in varying degrees of compression. Digital image editors are a must for a serious digital camera user.

See also

An image retrieval system is a computer system for browsing, searching and retrieving images from a large database of digital images. ... Suppose the smiley face in the top left corner is an RGB bitmap image. ... // Introduction Digital image processing is the use of computer algorithms to perform image processing on digital images. ... See also Category:Graphics file formats Here is a summary of the most common graphics file formats: Some file formats, e. ... This article needs to be cleaned up to conform to a higher standard of quality. ... Computer graphics (CG) is the field of visual computing, where one utilizes computers both to generate visual images synthetically and to integrate or alter visual and spatial information sampled from the real world. ... Suppose the smiley face in the top left corner is an RGB bitmap image. ...

External links

Adobe Photoshop Image Editor