Image editing

Many image editing programs are also used to render or create computer art from scratch.

Raster images are stored on a computer in the form of a grid of picture elements, or pixels.

The pixels can be changed as a group or individually by the sophisticated algorithms within the image editors.

However, vector graphics software, such as Adobe Illustrator, CorelDRAW, Xara Designer Pro or Inkscape, is used to create and modify vector images, which are stored as descriptions of lines, Bézier curves, and text instead of pixels.

Vector images can be modified more easily because they contain descriptions of the shapes for easy rearrangement.

Both cameras and computer programs allow the user to set the level of compression.

By contrast, the more popular JPEG file format uses a lossy compression algorithm (based on discrete cosine transform coding) by which the greater the compression, the more information is lost, ultimately reducing image quality or detail that can not be restored.

JPEG uses knowledge of the way the human visual system perceives color to make this loss of detail less noticeable.

Most graphics programs have several means of accomplishing this, such as: as well as more advanced facilities such as edge detection, masking, alpha compositing, and color and channel-based extraction.

This is a fundamental workflow that has become the norm for the majority of programs on the market today, and enables maximum flexibility for the user while maintaining non-destructive editing principles and ease of use.

Hence the use of the "green screen" technique (chroma key) which allows one to easily remove the background.

While this might also be useful for special effects, it is the preferred method of correcting the typical perspective distortion that results from photographs being taken at an oblique angle to a rectilinear subject.

The effect mimics the use of a perspective control lens, which achieves a similar correction in-camera without loss of definition.

Advanced photo enhancement software also supports many filters for altering images in various ways.

Graphics programs can be used to both sharpen and blur images in a number of ways, such as unsharp masking or deconvolution.

[16] Portraits often appear more pleasing when selectively softened (particularly the skin and the background) to better make the subject stand out.

[citation needed] 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.

It is widely used in the printing and photographic industries for increasing the local contrasts and sharpening the images.

When selecting a raster image that is not rectangular, it requires separating the edges from the background, also known as silhouetting.

This is useful to allow dynamic swapping via interactivity or animating parts of an image in the final presentation.

Image editors usually have a list of special effects that can create unusual results.

Using custom Curves settings[18] in Image editors such as Photoshop, one can mimic the "pseudo-solarisation" effect, better known in photographic circles as the Sabattier-effect.The Clone Stamp tool selects and samples an area of your picture and then uses these pixels to paint over any marks.

Grayscale conversion is useful for reducing the file size dramatically when the original photographic print was monochrome, but a color tint has been introduced due to aging effects.

Strictly speaking, the curves tool usually does more than simple gamma correction, since one can construct complex curves with multiple inflection points, but when no dedicated gamma correction tool is provided, it can achieve the same effect.

In addition, more complicated procedures, such as the mixing of color channels, are possible using more advanced graphics editors.

Advanced Dynamic Blending is a concept introduced by photographer Elia Locardi in his blog Blame The Monkey to describe the photographic process of capturing multiple bracketed exposures of a land or cityscape over a specific span of time in a changing natural or artificial lighting environment.

Once captured, the exposure brackets are manually blended together into a single High Dynamic Range image using post-processing software.

This means that while the final image may be a blend of a span of time, it visually appears to represent a single instant.