Image editing encompasses the processes of altering images, whether they be digital photographs, traditional analog photographs, or illustrations. An image (from Latin imago) or picture is an artifact usually two-dimensional that has a similar appearance to some subject &mdashusually Digital photography is a form of Photography that utilizes Digital technology to make Digital images of subjects Photographic processing is the Industrial process by which conventional Photographic film is treated after Photographic exposure in order to produce the An illustration is a visualization such as a Drawing, Painting, Photograph or other work of Art that stresses subject more than Before digital scanners and cameras became mainstream, traditional analog image editing was known as photo retouching, using tools such as an airbrush to modify photographs, or editing illustrations with any traditional art medium. Photo manipulation is the application of Image editing techniques to Photographs in order to create an Illusion or Deception (in contrast to mere An airbrush is a small air-operated tool that sprays various media including Ink and Dye, but most often Paint by a process of Nebulization In the Arts media (plural of Medium) are the materials and techniques used by an Artist to produce a work However, since the advent of digital images, analog image editing has become largely obsolete. Graphic software programs, which can be broadly grouped into vector graphics editors, raster graphics editors, and 3d modelers, are the primary tools with which a user may manipulate, enhance, and transform images. In Computer graphics, graphics software or image editing software is a program or collection of programs that enable a person to manipulate visual images A vector graphics editor is a Computer program that allows users to compose and edit Vector graphics Images interactively on the computer screen (compare A raster graphics editor is a Computer program that allows users to paint and edit Pictures interactively on the computer screen and save them in one 3D computer graphics software refers to programs used to create 3D Computer-generated imagery. Many image editing programs are also used to render or create computer art from scratch. Rendering in Visual art and Technical drawing means the process of creating shading and texturing of an image especially a Photorealistic one Computer art is any Art
Basics of image editing
Raster images are stored in a computer in the form of a grid of picture elements, or pixels. In Computer graphics, a raster graphics image or bitmap, is a Data structure representing a generally rectangular grid of Pixels In Digital imaging, a pixel ( pict ure el ement is the smallest piece of information in an image These pixels contain the image's color and brightness information. 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. In Mathematics, Computing, Linguistics and related subjects an algorithm is a sequence of finite instructions often used for Calculation The domain of this article primarily refers to bitmap graphics editors, which are often used to alter photographs and other raster graphics. However, vector graphics software, such as Adobe Illustrator or Inkscape, are used to create and modify vector images, which are stored as descriptions of lines, Bézier splines, and text instead of pixels. Vector graphics is the use of geometrical primitives such as points lines, Curves and shapes or Polygon (s which are all based Adobe Illustrator is a vector-based drawing program developed and marketed by Adobe Systems. Inkscape is a free and Open source Vector graphics editor application In the mathematical field of Numerical analysis, a Bézier curve is a Parametric curve important in Computer graphics and related fields TEXT is the band founded by Kristofer Steen David Sandström Fredrik Bäckström and Jon F Brännström It is easier to rasterize a vector image than to vectorize a raster image- how to go about vectorizing a raster image is the focus of much research in the field of computer vision. Rasterization or Rasterisation is the task of taking an image described in a Vector graphics format (shapes and converting it into a Raster image ( Computer vision is the science and technology of machines that see People like vector images because they are easy to modify, containing descriptions of the shapes in them for easy rearrangement, as well as scalable, being rasterizable at any resolution- to rasterize a vector image is simply to render it, while scaling a raster image up involves guessing at data that isn't there (see aliasing and other articles on information theory for more), and even scaling a raster image down involves guessing unless the scaling factor is an integer. Image resolution describes the detail an Image holds The term applies equally to Digital images film images and other types of images This article applies to signal processing including computer graphics Information theory is a branch of Applied mathematics and Electrical engineering involving the quantification of Information.
Editing programs
Due to the popularity of digital cameras, image editing programs are readily available. Many compact digital still cameras can record Sound and moving Video as well as still Photograph. Minimal programs, that perform such operations as rotating and cropping are often provided within the digital camera itself, while others are returned to the user on a compact disc (CD) when images are processed at a discount store. Cropping refers to the removal of the outer parts of an image to improve Framing, accentuate subject matter or change Aspect ratio. Many compact digital still cameras can record Sound and moving Video as well as still Photograph. A Compact Disc (also known as a CD) is an Optical disc used to store digital data, originally developed for storing digital audio The more powerful programs contain functionality to perform a large variety of advanced image manipulations. Popular raster-based digital image editors include Adobe Photoshop, GIMP, Corel Photo-Paint, Paint Shop Pro and Paint.NET. The GNU Image Manipulation Program, or GIMP, is a free Raster graphics editor used to process digital graphics and photographs Corel PHOTO-PAINT is a Raster graphics editor created by Corel. Paint Shop Pro ( PSP) is a Raster graphics editor and later in the series a Vector graphics editor for computers running the Microsoft Windows PaintNET is a raster graphics editing program for Windows, developed on the. For more, see: List of raster graphics editors. This is a comparison of Raster graphics editors sorted by availability
Digital data compression
Many image file formats use 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, such as those used in PNG file format, are lossless, which means no information is lost when the file is saved. Portable Network Graphics ( PNG) is a bitmapped image format that employs Lossless data compression. The JPEG file format uses a lossy compression algorithm- The greater the compression, the more information is lost, ultimately reducing image quality or detail. A lossy compression method is one where compressing data and then decompressing it retrieves data that may well be different from the original but is close enough to be useful JPEG uses knowledge of the way the brain and eyes perceive color to make this loss of detail less noticeable.
Image editor features
Listed below are some of the most used capabilities of the better graphic manipulation programs. The list is by no means all inclusive. There are a myriad of choices associated with the application of most of these features.
Selection
One of the prerequisites for many of the applications mentioned below is a method of selecting part(s) of an image, thus applying a change selectively without affecting the entire picture. Most graphics programs have several means of accomplishing this, such as a marquee tool, lasso, vector-based pen tools as well as more advanced facilities such as edge detection, masking, alpha compositing, and color and channel-based extraction.
Layers
Another feature common to many graphics applications is that of Layers, which are analogous to sheets of transparent acetate (each containing separate elements that make up a combined picture), stacked on top of each other, each capable of being individually positioned, altered and blended with the layers below, without affecting any of the elements on the other layers. Layers are used in Digital image editing to separate different elements of an image Layers are used in Digital image editing to separate different elements of an image Cellulose acetate, first prepared in 1865 is the Acetate Ester of Cellulose. This is a fundamental workflow which has become the norm for the majority of programs on the market today, and enables maximum flexibility for the user whilst maintaining non-destructive editing principles and ease of use.
Image size alteration
Image editors can resize images in a process often called image scaling, making them larger, or smaller. In computer graphics image scaling is the process of resizing a Digital image. High image resolution cameras can produce large images which are often reduced in size for Internet use. Image resolution describes the detail an Image holds The term applies equally to Digital images film images and other types of images The Internet is a global system of interconnected Computer networks Image editor programs use a mathematical process called resampling 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 which would equal 0. 3 megapixels. In Digital imaging, a pixel ( pict ure el ement is the smallest piece of information in an image
Cropping an image
Digital editors are used to crop images. Cropping refers to the removal of the outer parts of an image to improve Framing, accentuate subject matter or change Aspect ratio. Cropping creates a new image by selecting 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
Image editors have provisions to create an image histogram of the image being edited. An image histogram is type of Histogram which acts as a graphical representation of the tonal distribution in a Digital image. The histogram plots the number of pixels in the image (vertical axis) with a particular brightness value (horizontal axis). 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.
 Sunflower image |  Histogram of Sunflower image |
Noise removal
Image editors may feature a number of algorithms which can add or remove noise in an image. Image noise is a random usually unwanted variation in brightness or color information in an Image. JPEG artifacts can be removed; dust and scratches can be removed and an image can be de-speckled. Noise removal merely estimates the state of the scene without the noise and is not a substitute for obtaining a "cleaner" image. Excessive noise reduction leads to a loss of detail, and its application is hence subject to a trade-off between the undesirability of the noise itself and that of the reduction artifacts.
Noise tends to invade images when pictures are taken in low light settings. A new picture can be given an 'antiquated' effect by adding uniform monochrome noise.
Removal of unwanted elements
Most image editors can be used to remove unwanted branches, etc, using a "clone" tool. Removing these distracting elements draws focus to the subject, improving overall composition. In the Visual arts — in particular Painting, Graphic design, Photography and Sculpture — composition is the placement or arrangement
 Notice the branch in the original |  The eye is drawn to the center of the globe |
Selective color change
Some image editors have color swapping abilities to selectively change the color of specific items in an image, given that the selected items are within a specific color range.
Image orientation
 Image orientation: left–original; center–30° CCW rotation; right–flopped . A clockwise motion is one that proceeds 'like the Clock 's hands' from the top to the right then down and then to the left and back to the top |
Image editors are capable of altering an image to be rotated in any direction and to any degree. Mirror images can be created and images can be horizontally flipped or vertically flopped. "Mirror Image" is an episode of the Television series The Twilight Zone. A flipped image is a static or moving image that is generated by a mirror-reversal of an original across a horizontal axis A flopped image is a static or moving image that is generated by a mirror-reversal of an original across a vertical axis A small rotation of several degrees is often enough to level the horizon, correct verticality (of a building, for example), or both. This article describes the unit of angle For other meanings see Degree. The horizon ( Ancient Greek ὁ ὁρίζων, /ho horídzôn/ from ὁρίζειν, "to limit" is the apparent line that separates Rotated images usually require cropping afterwards, in order to remove the resulting gaps at the image edges. Cropping refers to the removal of the outer parts of an image to improve Framing, accentuate subject matter or change Aspect ratio.
Perspective correction and distortion
 Perspective correction: left–original, uncorrected right–perspective distortion removed. |
Some image editors allow the user to distort (or "transform") the shape of an image. A distortion is the alteration of the original shape (or other characteristic of an object image sound waveform or other form of information or representation While this might also be useful for special effects, it is the preferred method of correcting the typical perspective distortion which results from photographs being taken at an oblique angle to a rectilinear subject. Perspective (from Latin perspicere to see through in the graphic arts such as drawing is an approximate representation on a flat surface (such as paper of an image as it is perceived Care is needed while performing this task, as the image is reprocessed using interpolation of adjacent pixels, which may reduce overall image definition. In the mathematical subfield of Numerical analysis, interpolation is a method of constructing new data points within the range of a Discrete set of A definition is a statement of the meaning of a Word or Phrase. The effect mimics the use of a perspective correction lens, which achieves a similar correction in-camera without loss of definition. An in-camera effect is any Special effect in a video or movie that is created solely by using techniques in and on the Camera and/or its parts
Lens correction
Photo manipulation packages have functions to correct images for various lens distortions including pincushion, fisheye and barrel distortions. In Photography, a fisheye lens is a Wide-angle lens that takes in an extremely wide hemispherical image The corrections are in most cases subtle, but can improve the appearance of some photographs.
Sharpening and softening images
Graphics programs can be used to both sharpen and blur images in a number of ways, such as unsharp masking or deconvolution. Unsharp masking is an image manipulation technique now familiar to many users of digital image processing software but it seems to have been first used in Germany In Mathematics, deconvolution is an algorithm-based process used to reverse the effects of Convolution on recorded data [1] Portraits often appear more pleasing when selectively softened (particularly the skin and the background) to better make the subject stand out. This can be achieved with a camera by using a large aperture, or in the image editor by making a selection and then blurring it. Edge enhancement is an extremely common technique used to make images appear sharper, although purists frown on the result as appearing unnatural. Edge enhancement is a digital image processing filter that improves the apparent sharpness of an Image or Video.
Selecting and merging of images
Many graphics applications are capable of merging one or more individual images into a single file. The orientation and placement of each image can be controlled. The two images shown here were once individual studio portraits.
When selecting a raster image that is not rectangular, it requires separating the edges from the background, also known as silhouetting. This is the digital version of cutting out the image. Clipping paths may be used to add silhouetted images to vector graphics or page layout files that retain vector data. In 2D graphics In 2D computer graphics, a clipping path is a closed Vector path, or shape used to cut out an image in current Image editing Alpha compositing, allows for soft translucent edges when selecting images. In Computer graphics, alpha compositing is the process of combining an image with a background to create the appearance of partial transparency There are a number of ways to silhouette an image with soft edges including selecting the image or its background by sampling similar colors, selecting the edges by raster tracing, or converting a clipping path to a raster selection. Once the image is selected, it may be copied and pasted into another section of the same file, or into a separate file. The selection may also be saved in what is known as an alpha channel.
A popular way to create a composite image like this one is to use transparent layers. Layers are used in Digital image editing to separate different elements of an image In this case, the "background image" shown at left was placed as the bottom layer. The layer marked "Original Image" at left was then added as a second layer in a multi-layer document. Using an image layer mask, all but the girl are hidden from the layer, giving the impression that she has been added to the background layer. Layers are used in Digital image editing to separate different elements of an image Performing a merge in this manner preserves all of the pixel data on both layers to more easily enable future changes (such as adding the second individual) in the new merged image. In Digital imaging, a pixel ( pict ure el ement is the smallest piece of information in an image
Slicing of images
A more recent tool in digital image editing software is the image slicer. Parts of images for graphical user interfaces or web pages are easily sliced, labeled and saved separately from whole images so the parts can be handled individually by the display medium. This is useful to allow dynamic swapping via interactivity or animating parts of an image in the final presentation.
- See also: Slicing (web design)
Special effects
Image editors usually have a list of special effects that can create unusual results. Images may 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
 example of six colers and greyscale and noise, created in Paint Shop Pro 7 |
It is possible, using software, to change the color depth of images. Color depth. or bit depth, is a Computer graphics term describing the number of Bits used to represent the Color of a single Pixel Common color depths are 2, 4, 16, 256, 65. 5 thousand and 16. 7 million colors. The JPEG and PNG image formats are capable of storing 16. 7 million colors (equal to 256 luminance values per color channel). In addition, grayscale images of 8 bits or less can be created, usually via conversion and down-sampling from a full color image. In Computing, a grayscale or greyscale Digital image is an image in which the value of each Pixel A bit is a binary digit, taking a value of either 0 or 1 Binary digits are a basic unit of Information storage and communication
Contrast change and brightening
Image editors have provisions to change the contrast of images and brighten or darken the image. Underexposed images can be often be improved by using this feature. Recent advances have allowed more intelligent exposure correction whereby only pixels below a particular luminosity threshold are brightened, thereby brightening underexposed shadows without affecting the rest of the image.
Color adjustments
The color of images can be altered in a variety of ways. Colors can be faded in and out, and tones can be changed using curves or other tools. In Image editing, a curve is a remapping of image tonality specified as a function from input level to output level used as a way to emphasize colours or other elements The color balance can be improved, which is important if the picture was shot indoors with daylight film, or shot on a camera that with an incorrectly adjusted white balance. In Photography and Image processing, color balance is the global adjustment of the intensities of the colors (typically red green and blue Primary colors Special effects, like sepia and grayscale can be added to an image. In addition, more complicated procedures such as the mixing of color channels are possible using more advanced graphics editors.
The red-eye effect, which occurs when flash photos are taken when the pupil is too widely open (thus reflecting back the color of the blood-rich retina), can also be eliminated at this stage. The red-eye effect in Photography is the common appearance of Red Pupils in color Photographs of Eyes It occurs when using a photographic
Printing
Controlling the print size and quality of digital images requires an understanding of the pixels-per-inch (ppi) variable that is stored in the image file and sometimes used to control the size of the printed image. Within the Image Size dialog (as it is called in Photoshop), the image editor allows the user to manipulate both pixel dimensions and the size of the image on the printed document. These parameters work together to produce a printed image of the desired size and quality. Pixels per inch of the image, pixel per inch of the computer monitor, and dots per inch on the printed document are related, but in use are very different. The Image Size dialog can be used as an image calculator of sorts. For example, a 1600 x 1200 image with a ppi of 200 will produce a printed image of 8 x 6 inches. The same image with a ppi of 400 will produce a printed image of 4 x 3 inches. Change the ppi to 800, and the same image now prints out at 2 x 1. 5 inches. All three printed images contain the same data (1600 x 1200 pixels) but the pixels are closer together on the smaller prints, so the smaller images will potentially look sharp when the larger ones do not. The quality of the image will also depend on the capability of the printer.
See also
- Adobe Photoshop
- Color space
- Comparison of raster graphics editors
- Computer graphics
- Curve (tonality)
- Digital darkroom
- Digital image processing
- Digital painting
- Dynamic imaging
- Graphics file format summary
- Graphic art software
- Homomorphic filtering
- Image development (visual arts)
- Image distortion
- Image processing
- Image retrieval
- Image warping
- Layers (digital image editing)
- Photo manipulation
- Photoshop contest
- Raster graphics
References
- ^ Implementations include FocusMagic, and Photoshop
- "Fantasy, fairy tale and myth collide in images: By digitally altering photos of landscapes, artist Anthony Goicolea creates an intriguing world," The Vancouver Sun (British Columbia); June 19, 2006. A Color model is an abstract mathematical model describing the way Colors can be represented as Tuples of numbers typically as three or four values or color components This is a comparison of Raster graphics editors sorted by availability Computer graphics are Graphics created by Computers and more generally the Representation and Manipulation of Pictorial Data In Image editing, a curve is a remapping of image tonality specified as a function from input level to output level used as a way to emphasize colours or other elements See also Digital darkroom. Digital Darkroom was an innovative award-winning Apple Macintosh Graphics program for editing Digital image processing is the use of computer Algorithms to perform Image processing on Digital images As a subfield of Digital signal processing Digital painting is an emerging art form in which traditional painting techniques such as Watercolor, oils, Impasto, etc Dynamic imaging is the amalgamation of Digital imaging and Workflow automation. This is a comparison of Image file formats. General Ownership of the format and related information Graphic art software is a subclass of Application software used for Graphic design, Multimedia development specialized image development, general Homomorphic filtering is a generalized technique for signal and image processing involving a nonlinear mapping to a different domain in which linear filter techniques are applied followed Term Scope Image development is essentially Visual art usually for commercial purposes, but includes techniques not considered Fine art or Image processing is any form of Signal processing for which the input is an image such as photographs or frames of video the output of image processing can be either an image An image retrieval system is a computer system for browsing searching and retrieving images from a large Database of Digital images Most traditional and common methods Image warping is the process of digitally manipulating an image such that any shapes portrayed in the image have been significantly distorted Layers are used in Digital image editing to separate different elements of an image Photo manipulation is the application of Image editing techniques to Photographs in order to create an Illusion or Deception (in contrast to mere A Photoshop contest, or sometimes photochop contest, is an Online game in which a Website or user of an In Computer graphics, a raster graphics image or bitmap, is a Data structure representing a generally rectangular grid of Pixels
- "It's hard to tell where pixels end and reality begins," The San Francisco Chronicle; September 26, 2006.
- "Virtual Art: From Illusion to Immersion," MIT Press 2002; Cambridge, Mass.
External links
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