Pantone catalog. Color depth. Color depth or colour depth (see spelling differences), also known as bit depth, is either the number of bits used to indicate the color of a single pixel, in a bitmapped image or video frame buffer, or the number of bits used for each color component of a single pixel.[1][2][3][4] For consumer video standards, such as High Efficiency Video Coding (H.265), the bit depth specifies the number of bits used for each color component.[1][2][3][4] When referring to a pixel the concept can be defined as bits per pixel (bpp), which specifies the number of bits used.
When referring to a color component the concept can be defined as bits per channel (bpc), bits per color (bpc), or bits per sample (bps).[1][2][5] Color depth is only one aspect of color representation, expressing how finely levels of color can be expressed (a.k.a. color precision); the other aspect is how broad a range of colors can be expressed (the gamut).
Indexed color[edit] 2 bits (4 colors) 4 bits (16 colors) 8 bits (256 colors) Posterization. Example of a photograph in JPEG format (24-bit color or 16.7 million colors) before posterization, contrasting the result of saving to GIF format (256 colors). Posterization occurs across the image, but is most obvious in areas of subtle variation in tone. Posterization of an image entails conversion of a continuous gradation of tone to several regions of fewer tones, with abrupt changes from one tone to another. This was originally done with photographic processes to create posters. It can now be done photographically or with digital image processing, and may be deliberate or may be an unintended artifact of color quantization. Cause[edit] The effect may be created deliberately, or happen accidentally. Unwanted posterization, also known as banding, may occur when the color depth, sometimes called bit depth, is insufficient to accurately sample a continuous gradation of color tone.
Photographic process[edit] Applications[edit] Posterizing time [edit] See also[edit] References[edit] Color space. A comparison of the chromaticities enclosed by some color spaces. 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 (e.g. RGB and CMYK are color models). However, a color model with no associated mapping function to an absolute color space is a more or less arbitrary color system with no connection to any globally understood system of color interpretation. Adding a certain mapping function between the color model and a certain reference color space results in a definite "footprint" within the reference color space. This "footprint" is known as a gamut, and, in combination with the color model, defines a new color space.
In the most generic sense of the definition above, color spaces can be defined without the use of a color model. Understanding the concept[edit] A comparison of RGB and CMYK color models. Notes[edit] Conversion[edit] Density[edit] Generic color models[edit] Palette (computing) Palette (computing) Color depth. Downsampling. Downsampling by an integer factor[edit] Downsampling by an integer factor, M, can be explained as a 2-step process, with an equivalent implementation that is more efficient: Reduce high-frequency components with a digital lowpass filter.Decimate the output sequence, keeping only every Mth output sample. Decimation causes high-frequency signal components to be misinterpreted by subsequent users of the data, which is a form of distortion called aliasing.
The first step, if necessary, is to suppress such components to an acceptable level of distortion. In this application, the filter is called an anti-aliasing filter, and its design is discussed below. When the anti-aliasing filter is an IIR design, it relies on feedback from output to input, prior to the decimation step. Where the h[•] sequence is the impulse response, and K is its length. x[•] represents the input sequence being downsampled. Fig.1: Spectral effects of decimation compared on 3 popular frequency scale conventions Notes[edit] Web colors. Web colors are colors used in displaying web pages, and the methods for describing and specifying those colors. Colors may be specified as an RGB triplet or in hexadecimal format (a hex triplet).
They may also be specified according to their common English names in some cases. Often a color tool or other graphics software is used to generate color values. In some uses, hexadecimal color codes are specified with notation using a leading number sign (#).[1][2] A color is specified according to the intensity of its red, green and blue components, each represented by eight bits. Thus, there are 24 bits used to specify a web color, and 16,777,216 colors that may be so specified.
Hex triplet[edit] A hex triplet is a six-digit, three-byte hexadecimal number used in HTML, CSS, SVG, and other computing applications, to represent colors. Byte 1: red value (color type red) Byte 2: green value (color type green) Byte 3: blue value (color type blue) Shorthand hexadecimal form[edit] HTML color names[edit] Colour look-up table. A colour look-up table (CLUT) is a mechanism used to transform a range of input colours into another range of colours.
It can be a hardware device built into an imaging system or a software function built into an image processing application. The hardware colour look-up table will convert the logical colour (pseudo-colour) numbers stored in each pixel of video memory into physical colours, normally represented as RGB triplets, that can be displayed on a computer monitor. The colour palette is simply a block of fast RAM which is addressed by the logical colour and whose output is split into the red, green, and blue levels which drive the actual display (e.g., a CRT or cathode ray tube). A CLUT is characterized by: A common example would be a palette of 256 colours (e.g. VGA hardware); that is, the number of entries is 256, and thus each entry is addressed by an 8-bit pixel value. The 8 bits is known as colour depth, bit depth or bits per pixel (bpp). An abstract, graphic example would be: List of color palettes. Only a sample and the palette's name are given here.
More specific articles are linked from the name of each palette, for the test charts, samples, simulated images, and further technical details (including references). In the past, manufacturers have developed many different display systems in a competitive, non-collaborative basis (with a few exceptions, as the VESA consortium), creating many proprietary, non-standard different instances of display hardware. Often, as with early personal and home computers, a given machine employed its unique display subsystem, with its also unique color palette. Also, software developers had made use of the color abilities of distinct display systems in many different ways. The result is that there is no single common standard nomenclature or classification taxonomy which can encompass every computer color palette.
In order to organize the material, color palettes have been grouped following arbitrary but rational criteria. Monochrome palettes[edit] Graphic design. Graphic design is the methodology of visual communication, and problem-solving through the use of type, space and image. The field is considered a subset of visual communication and communication design, but sometimes the term "graphic design" is used interchangeably with these due to overlapping skills involved. Graphic designers use various methods to create and combine words, symbols, and images to create a visual representation of ideas and messages. A graphic designer may use a combination of typography, visual arts and page layout techniques to produce a final result. Graphic design often refers to both the process (designing) by which the communication is created and the products (designs) which are generated.
History[edit] Page from the Book of Kells: Folio 114v, Decorated text. The advent of printing[edit] During the Tang Dynasty (618–907) between the 7th and 9th century AD, wood blocks were cut to print on textiles and later to reproduce Buddhist texts. Applications[edit] Colorimetry and printing | Metropack. Colour control is today an important parameter in quality control processes (goods-in checking, lab tests, production tests, finished product tests…). It may be used by different types of operators where their test parameters may differ. The results of the analyses may be used internally or sent to a supplier or client. The figures obtained may be used to accept or to modify the colours or for an absolute quantification for an analytic traceability of the information. Beyond colour specifications, we are able to perform various tests such as abrasion, or study the ageing of the products on the shelves in order to tests the quality of the materials and the printing.
Color tool. A screenshot of the GTK+ color picker. A color tool, color picker, or color chooser is a utility, usually found within graphics software or online, used to choose colors or create color schemes. Many such tools exist on the world wide web which include features such as a color harmonization interface, a color picker, RGB and HSL conversion and manipulation, a collection of saved schemes, and other similar characteristics. Designers, developers, and other professionals that work with other types of screen or print media use these tools in their work. Purpose[edit] Interface[edit] Color tools can vary in their interface. Some may use sliders, buttons, text boxes for color values, or direct manipulation. Each color is represented as a unique number. See also[edit] External links[edit] RGBHEXCODE Color Picker.