The image processing is the change of photos, negatives, slides or digital images. Often, the image processing is applied to in order to eliminate errors that can occur when photographing or other image acquisitions. These include over-and under-exposure, blur, contrast weakness, image noise, red- eye effect, converging lines, etc. Due to these errors affect images often too dark, too bright, too blurry or otherwise deficient. The causes, technical problems or poor-quality recording equipment (digital camera, lens, scanner ) to be the incorrect operation and unfavorable working conditions or poor templates. The two images on the right show some possibilities of image processing: The top image looks overexposed, tinted, the text of focus, the object shows up a light reflex and is outside the center. The lower, corrected, now clean color image on the other hand looks much clearer and clearer. Because the image object is stressed, but he is bigger, equalized and centered in the frame, the format was slightly adjusted in height.
Types of image processing
The image processing includes different techniques such as retouching, unsharp masking, dodging and other optimization methods.
In digital image processing is the computer-aided processing of digital images, usually raster graphics, mostly photos or scanned documents.
The traditional image processing includes photographs, negatives and Diabearbeitung. For this type of image processing special equipment, materials, chemicals and knowledge are necessary.
The hybrid image processing includes methods of traditional and digital image processing and has been developed in the 1990s. While the film is fully exposed in the enlarger, there is a special translucent sheet between film and photo. This disk can be partially rendered opaque by electric current. In a split second can be post-exposed Burns or masked blurred.
Today - digital - form of image processing is an inhomogeneous conglomerate of various precursors. Example, the following precursor as main areas may be mentioned:
All areas have left their own traces, for example:
Same concepts that mean different things:
And terms that are not clear:
Due to the dominance of some image editing programs ( in the professional sector especially Adobe Photoshop ) Here is gradually a uniform vocabulary. Alternative standardization efforts are to find very few, since a large part of the discussion is led by amateurs.
On the software that is used in the field of image processing, graphics software will be discussed in the article.
Some possibilities of digital image processing
The software by which the image processing takes place, is called image-editing program. It provides various editing features, most of which are located in an application menu, a toolbar, or toolbar. Examples are:
- Dodging and burning: By dodging and dodging ( engl. Dodge and Burn ) is corrected the exposure.
- Select: Certain areas of the image can be, for example, rectangular, circular or partially marked and thereby selected. These areas can then be edited separately from other image sections. For selections, there are different selection tools, on the one hand geometrically defined as a rectangle, ellipse, etc., on the other hand, certain tools such as lasso tool or magic wand.
- Automatic corrections: For beginners and newcomers to the image processing provide image editing programs to automatic corrections. With these various areas, such as the contrast, color and tone can be corrected by pressing a button. In contrast to the handwritten correction, the results of the automatic correction, however, are to be regarded rather sober.
- Beauty retouching is the extreme stylization of portraits - to be various techniques used in the main digital retouching techniques.
- Exposure Compensation: With various tools of exposure correction can be corrected over - or under-exposed images. Exposure compensation is carried out globally over brightness and contrast, over the curve ( Levels ) or partially by dodging and burning.
- Colorkey: describes the cropping of pixels in the Video-/Filmnachbearbeitung, see also keying.
- File Format: conversion or storage in a specific graphic format. A distinction is made, inter alia, JFIF, PNG, GIF, TIFF, or JPEG2000 format. For the storage of layers, masks and channels, the PSD or XCF format is.
- Turning: turning an image The error can be eliminated or special effects. Easy Turn is particularly at a horizon "leaning " attached.
- Levels: Different image elements can be arranged as transparencies above the other. The individual elements are arranged on different levels and edited individually. Layers can be locked to prevent accidental editing or deleting. By exchanging layers objects are moved into the foreground or background.
- Exif information: The display of Exif information, such as the time, digital camera manufacturers and digital camera data. Other metadata, such as the IPTC -NAA standard can, show up.
- Colors: Colors play an important role in image processing. The color can be changed, the color saturation in each case adapted and color casts are removed. On the other hand, it is also the colors of an image beyond, for example, for creating black and white images. A distinction is made between the colors of the subtractive and additive color mixing. Here are color models and color spaces like RGB, CMYK, L * a * b and HSB the description of colors. The cross effect refers to a subsequent movement of the color spectrum.
- Color mode and color depth: you can convert an image to a desired color mode or image mode. We distinguish the modes: bitmap, grayscale, duplex, indexed color, RGB, Lab and CMYK. Depending on the color mode you will see a different color depth. It differs in color depth between true color, high color and indexed color, but also between grayscale and black and white.
- Filters: Images can be edited with a variety of graphic filters and alienated: commonly used blur and sharpness filter (eg edge enhancement ). Filters with more artistic effects include relief effects, lighting effects, shadow effects, Blur. Furthermore, there is the possibility of expanding graphics filters by plug-ins.
- Forms: Used for the production of geometric objects such as rectangles, ellipses or polygons; but also for creating a pattern forms such as speech, symbols etc.
- Photomontage: The photomontage, also called " Composing ", several images are combined to form a kind of composition. Thus, for example, individual image objects are selected and copied into another image. See also photo collage.
- Photo Mosaic: When a photomosaic image of lots of juxtaposed photos is created.
- Cropping: Useless image portions are removed in order to emphasize an object. The exemption of images is one of the essential tasks of image processing.
- Fill: The fill tool is used to fill an entire image or only a section of the screen with a desired color.
- Gamma correction: In a gamma correction, the lighting and the colors can be changed.
- Gradation: With a tone curve, contrast and brightness can be changed.
- Histogram: A histogram, the brightness range of an image is displayed. The plays, inter alia, Levels in an important role.
- Invert: When inverting the colors are reversed.
- Channels: A color channel indicates that each basic color using a color channel. Im CMYK' mode, there are four channels (cyan, magenta, yellow, and black) and RGB ' the primary colors: red, green and blue. Furthermore, alpha channels are distinguished here selections and masks can be saved.
- Tilting: Tilting perspective problems can be resolved in an image.
- Colorize: When Colorize images or image portions are changed in color; in contrast to the color key Grayscale images are usually dyed afterwards.
- Converting image files to different file formats and image formats. See also file format.
- Clone Stamp tool: Used for correcting blemishes and for transmitting image sections in other areas. If used heavily in portrait retouching.
- Correction of brightness, contrast and tonal value (also for generating high-key or low-key character )
- Lasso: The Lasso image regions are selected.
- Macros: A sequence of processing steps can be saved as a macro to be applied as often as required on any images.
- Painting: One of the most basic functions of image editing programs is the opportunity to paint. This can be simulated by using different brushes painting techniques. Should distinguish between one painting and drawing. When painting pixels are generated, while drawing not against it. For drawing we therefore used paths with them can create vector elements.
- Masking: When masking certain areas are selected to protect them from editing. The mask can be expanded in menu mode with the brush or reduced with the eraser. Errors can be easily reversible in menu mode.
- Monochrome: The production of monochrome images can be easily performed using an image editing program.
- Panorama: For single images, for example in a large landscape, can create a panoramic image. There are also special stitching software.
- Paths: With image editing programs can also draw vector elements. Paths are used here to create simple vector elements. If one wants to create more complex drawings, however, one should resort to vector graphics programs. One should consider further that arise when drawing, as opposed to painting with a brush, no pixels.
- Brush: The brush has become the universal brush: brush tip size and can be selected, it can be chosen a color or filled with a pattern. Particular use is the brush for digital painting.
- Pipette: The pipette used for color determination and color photograph.
- Eraser: removal of image information with various Radiergummispitzen.
- Undo steps that allow can be undone with the Undo function.
- Sharpen: When sharpening the sharpness of an image or of individual parts of the image is increased. The dominant method is called unsharp masking.
- Scale: Images can be enlarged or reduced by various methods or.
- Solarization: In the electronic solarization the colors of pixels whose brightness is above a set limit are inverted.
- Mirrors: mirror (horizontal or vertical) is often used for the correction of the scanned negative or for the fitting of images in a layout.
- Batch processing: functions and / or macros are automatically carried out in several image files. Especially for digital photo albums, this feature is very useful. Thus, for example the image size, resolution, etc. are changed, which saves a lot of work as opposed to individual processing.
- Texts: With a text tool to texts of various kinds on an image can be created, where there are many text effects, such as relief, etc., are.
- Toning: A black and white image is inked. The most popular toning is sepia.
- Levels: Levels can be corrected with a range of hues. The histogram is used as a tool by showing the light and dark areas. The brightness, contrast and color saturation can then be specifically corrected.
- Change the file size ( image compression ), the resolution or image resolution, for example, the use of images on the Internet.
- History: With curves you create color transitions.
- Blur: The blur the image or individual parts of the image are blurred, for example, to cover an unsuitable background. This blurring but can be as generate motion blur, for example, effects.
- Magic Wand: marking tool that selects all pixels that are adjacent to the pixel you click and have a similar shade and a similar brightness. Is often used to select the background.
- Drawing: will you draw, as opposed to paint, does not generate pixels, but vectors. Here are paths to create vector elements.
- Zoom: For many processing steps, it is necessary: approaching closer to the subject, for example to remove image defects.
Applications of the image processing
The digital image processing has been widely used due to the possibilities of digital photography, which allows quick, responsive shooting and transferring the images to the PC. Many image editing programs ( "Graphics Software") are tailored to the home user area by providing simplified correction capabilities among others. In professional fields, the image processing is used, among other photographers, designers and media professionals in the desktop publishing area and prepress. The changes in the image processing images in publications - published all kinds, for example, in magazines, catalogs and books - print and digital media.
Imaging can also be used specifically for photo manipulation. Typical examples are the processing of faces to make wrinkles and other " blemishes " disappear, and removing unwanted people from an image. The boundaries between legitimate and illegitimate image editing photo manipulation are fluid; an assessment must be made in individual cases.
The image processing is also a way of artistic development - inter alia in the fields of digital art and media art.