A binary image is one that consists of pixels that can have one of exactly two colors, usually black and white. Binary images are also called ''bi-level'' or ''two-level'',
Pixelart made of two colours is often referred to as ''1-Bit'' or ''1bit''. This means that each pixel is stored as a single bit—i.e., a 0 or 1. The names ''black-and-white'', ''B&W'',
monochrome
A monochrome or monochromatic image, object or palette is composed of one color (or values of one color). Images using only shades of grey are called grayscale (typically digital) or black-and-white (typically analog). In physics, monochrom ...
or
monochromatic
A monochrome or monochromatic image, object or color scheme, palette is composed of one color (or lightness, values of one color). Images using only Tint, shade and tone, shades of grey are called grayscale (typically digital) or Black and wh ...
are often used for this concept, but may also designate any images that have only one sample per pixel, such as
grayscale images. In
Photoshop
Adobe Photoshop is a raster graphics editor developed and published by Adobe Inc. for Windows and macOS. It was originally created in 1988 by Thomas and John Knoll. Since then, the software has become the industry standard not only in raster ...
parlance, a binary image is the same as an image in "Bitmap" mode.
Binary images often arise in
digital image processing
Digital image processing is the use of a digital computer to process digital images through an algorithm. As a subcategory or field of digital signal processing, digital image processing has many advantages over analog image processing. It allo ...
as
masks
A mask is an object normally worn on the face, typically for protection, disguise, performance, or entertainment and often they have been employed for rituals and rights. Masks have been used since antiquity for both ceremonial and practi ...
or
thresholding, and
dither
Dither is an intentionally applied form of image noise, noise used to randomize quantization error, preventing large-scale patterns such as color banding in images. Dither is routinely used in processing of both digital audio and digital vide ...
ing. Some input/output devices, such as
laser printer
Laser printing is an electrostatic digital printing process. It produces high-quality text and graphics (and moderate-quality photographs) by repeatedly passing a laser beam back and forth over a negatively-charged cylinder called a "drum" to d ...
s,
fax machines
Fax (short for facsimile), sometimes called telecopying or telefax (the latter short for telefacsimile), is the telephonic transmission of scanned printed material (both text and images), normally to a telephone number connected to a printer o ...
, and bilevel
computer displays
A computer monitor is an output device that displays information in pictorial or textual form. A discrete monitor comprises a electronic visual display, visual display, support electronics, power supply, Housing (engineering), housing, electric ...
, can only handle bilevel images.
A binary image can be stored in memory as a
bitmap
In computing, a bitmap is a mapping from some domain (for example, a range of integers) to bits. It is also called a bit array
A bit array (also known as bitmask, bit map, bit set, bit string, or bit vector) is an array data structure that c ...
, a packed array of bits. A 640×480 image requires 37.5
KiB
The byte is a unit of digital information that most commonly consists of eight bits. Historically, the byte was the number of bits used to encode a single character of text in a computer and for this reason it is the smallest addressable unit ...
of storage. Because of the small size of the image files, fax machine and document management solutions usually use this format. Most binary images also compress well with simple
run-length compression schemes.
Binary images can be interpreted as
subset
In mathematics, Set (mathematics), set ''A'' is a subset of a set ''B'' if all Element (mathematics), elements of ''A'' are also elements of ''B''; ''B'' is then a superset of ''A''. It is possible for ''A'' and ''B'' to be equal; if they are ...
s of the
two-dimensional integer lattice ''Z''
2; the field of
morphological image processing
Mathematical morphology (MM) is a theory and technique for the analysis and processing of geometrical structures, based on set theory, lattice theory, topology, and random functions. MM is most commonly applied to digital images, but it can be empl ...
was largely inspired by this view.
Operations on binary images
An entire class of operations on binary images operates on a 3×3 window of the image. This contains nine pixels, so 2
9 or 512 possible values. Considering only the central pixel, it is possible to define whether it remains set or unset, based on the surrounding pixels. Examples of such operations are thinning, dilating, finding branch points and endpoints, removing isolated pixels, shifting the image a pixel in any direction, and breaking H-connections.
Conway's Game of Life
The Game of Life, also known simply as Life, is a cellular automaton devised by the British mathematician John Horton Conway in 1970. It is a zero-player game, meaning that its evolution is determined by its initial state, requiring no further ...
is also an example of a 3×3 window operation.
Another class of operations is based on the notion of filtering with a structuring element. The structuring element is binary image, usually small, which is passed over the target image, in a similar manner to a filter in gray scale image processing. Since the pixels can only have two values, the morphological operations are
erosion
Erosion is the action of surface processes (such as water flow or wind) that removes soil, rock, or dissolved material from one location on the Earth's crust, and then transports it to another location where it is deposited. Erosion is distin ...
(any unset pixels within the structuring element cause the pixel to be unset) and
dilation
Dilation (or dilatation) may refer to:
Physiology or medicine
* Cervical dilation, the widening of the cervix in childbirth, miscarriage etc.
* Coronary dilation, or coronary reflex
* Dilation and curettage, the opening of the cervix and surgic ...
(any set pixels within the structuring element cause the pixel to be set). Important operations are
morphological opening and
morphological closing which consist of erosion followed by dilation and dilation followed by erosion, respectively, using the same structuring element. Opening tends to enlarge small holes, remove small objects, and separate objects. Closing retains small objects, removes holes, and joins objects.
A very important characteristic of a binary image is the
distance transform
A distance transform, also known as distance map or distance field, is a derived representation of a digital image. The choice of the term depends on the point of view on the object in question: whether the initial image is transformed into another ...
. This gives the distance of every set pixel from the nearest unset pixel. The distance transform can be efficiently calculated. It allows efficient computation of
Voronoi diagrams
In mathematics, a Voronoi diagram is a partition of a plane into regions close to each of a given set of objects. In the simplest case, these objects are just finitely many points in the plane (called seeds, sites, or generators). For each seed t ...
, where each pixel in an image is assigned to the nearest of a set of points. It also allows skeletonization, which differs from thinning in that skeletons allow recovery of the original image. The distance transform is also useful for determining the center of the object, and for matching in image recognition.
Another class of operations is gathering orientation-free metrics. This is often important in image recognition where the orientation of the camera needs to be removed. Orientation-free metrics of a group of connected or surrounded pixels include the
Euler number
In mathematics, the Euler numbers are a sequence ''En'' of integers defined by the Taylor series expansion
:\frac = \frac = \sum_^\infty \frac \cdot t^n,
where \cosh (t) is the hyperbolic cosine function. The Euler numbers are related to a ...
, the perimeter, the area, the compactness, the area of holes, the minimum radius, the maximum radius.
Image segmentation
Binary images are produced from color images by
segmentation. Segmentation is the process of assigning each pixel in the source image to two or more classes. If there are more than two classes then the usual result is several binary images. The simplest form of segmentation is probably
Otsu's method
In computer vision and image processing, Otsu's method, named after , is used to perform automatic image thresholding. In the simplest form, the algorithm returns a single intensity threshold that separate pixels into two classes, foreground a ...
which assigns pixels to foreground or background based on grayscale intensity. Another method is the
watershed algorithm In the study of image processing, a watershed is a transformation defined on a grayscale image. The name refers metaphorically to a geological drainage divide, ''watershed'', or drainage divide, which separates adjacent drainage basins. The watershe ...
.
Edge detection
Edge detection includes a variety of mathematical methods that aim at identifying edges, curves in a digital image at which the image brightness changes sharply or, more formally, has discontinuities. The same problem of finding discontinuitie ...
also often creates a binary image with some pixels assigned to edge pixels, and is also a first step in further segmentation.
Skeletons
Thinning or skeletonization produces binary images which consist of pixel-wide lines. The branchpoints and endpoints can then be extracted, and the image converted to a graph. This is important in image recognition, for example in
optical character recognition
Optical character recognition or optical character reader (OCR) is the electronic or mechanical conversion of images of typed, handwritten or printed text into machine-encoded text, whether from a scanned document, a photo of a document, a scen ...
.
Interpretation
The interpretation of the pixel's binary value is also device-dependent. Some systems interprets the bit value of 0 as black and 1 as white, while others reversed the meaning of the values. In the
TWAIN
Twain may refer to:
People
* Mark Twain, pen name of American writer Samuel Langhorne Clemens (1835–1910)
* Norman Twain (1930–2016), American film producer
* Shania Twain (born 1965), Canadian singer-songwriter
Places
* Twain, California, a ...
standard PC interface for
scanners
''Scanners'' is a 1981 Canadian science fiction horror film written and directed by David Cronenberg and starring Stephen Lack, Jennifer O'Neill, Michael Ironside, and Patrick McGoohan. In the film, "scanners" are psychics with unusual telepathic ...
and
digital camera
A digital camera is a camera that captures photographs in digital memory. Most cameras produced today are digital, largely replacing those that capture images on photographic film. Digital cameras are now widely incorporated into mobile device ...
s, the first flavor is called ''
vanilla
Vanilla is a spice derived from orchids of the genus ''Vanilla (genus), Vanilla'', primarily obtained from pods of the Mexican species, flat-leaved vanilla (''Vanilla planifolia, V. planifolia'').
Pollination is required to make the p ...
'' and the reversed one ''chocolate''.
Dither
Dither is an intentionally applied form of image noise, noise used to randomize quantization error, preventing large-scale patterns such as color banding in images. Dither is routinely used in processing of both digital audio and digital vide ...
ing is often used for displaying
halftone
Halftone is the reprographic
Reprography (a portmanteau of ''reproduction'' and ''photography'') is the reproduction of graphics through mechanical or electrical means, such as photography or xerography. Reprography is commonly used in catal ...
images.
1-Bit in digital art
Binary
pixelart, better known as ''1-Bit'' or ''1bit'' art, has been a method of displaying graphics since early computers. While early computers such as the
zx81
The ZX81 is a home computer that was produced by Sinclair Research and manufactured in Dundee, Scotland, by Timex Corporation. It was launched in the United Kingdom in March 1981 as the successor to Sinclair's ZX80 and designed to be a low-cost ...
used the restriction as a necessity of the hardware, hand-held LCD games such as
Game & Watch
The Game & Watch brand ( ''Gēmu & Uotchi''; called ''Tricotronic'' in West Germany and Austria, abbreviated as ''G&W'') is a series of handheld electronic games developed, manufactured, released, and marketed by Nintendo from 1980 in video gam ...
and
Tamagotchi
The is a handheld digital pet that was created in Japan by Akihiro Yokoi of WiZ and Aki Maita of Bandai. It was released by Bandai on November 23, 1996 in Japan and in the USA on May 1, 1997, quickly becoming one of the biggest toy fads o ...
, alongside early computers with a focus on graphic user interfaces like the
Macintosh
The Mac (known as Macintosh until 1999) is a family of personal computers designed and marketed by Apple Inc., Apple Inc. Macs are known for their ease of use and minimalist designs, and are popular among students, creative professionals, and ...
made large steps in promoting the culture, technique and aesthetic of the restrictions of 1-bit art.
Modern examples of 1bit art are visible in indie videogames and other digital art. Best-seller games like ''
Gato Roboto'', ''
Return of the Obra Dinn
''Return of the Obra Dinn'' is an adventure game, adventure and puzzle video game created by American video game designer Lucas Pope, and published by Japanese studio 3909. It was his second commercial game, following 2013's ''Papers, Please'', ...
'', ''
Minit'' and ''
World of Horror
''World of Horror'', also known by its Japanese title , is a role-playing video game with a 1-bit pixel art style, inspired by the works of H. P. Lovecraft and Junji Ito. The game was created by Polish developer Paweł Koźmiński, and published ...
'' use 1bit as a style to give their games a retro feel or to simply save the graphic designers time in development. There is even new 1-Bit hardware in development, such as the experimental handheld console
Playdate.
For pixel artists, 1-Bit has become a common challenge for creating art. The pixelart contest ''Pixtogether'' required its participants to use only two colours for its 10th monthly contest. Not a lot of artists mainly do 1bit art, but many of them stay in contact with each other to exchange knowledge about working with the restriction, and hosting own collaborations.
Brandon James Greer, who makes popular youtube tutorials on 1bit and other pixel artwork, says that "the restriction leads to some unique approaches" and that working in 1-Bit is "a very fun and unique challenge".
[Archived a]
Ghostarchive
and th
Wayback Machine
While 1bit can be called an
art style
''Art Style'' is a video game series created by skip Ltd. for WiiWare and DSiWare. The first game in the ''Art Style'' series, ''Orbient'', was released for WiiWare in September 2008. Another two ''Art Style'' games, ''Cubello'' and ''Rotohex'', ...
itself, each piece falls under a second style too. Obvious differences in 1bit art styles are for example whether, how much and what kind of
dithering
Dither is an intentionally applied form of noise used to randomize quantization error, preventing large-scale patterns such as color banding in images. Dither is routinely used in processing of both digital audio and video data, and is often ...
is being used, the
image resolution
Image resolution is the detail an image holds. The term applies to digital images, film images, and other types of images. "Higher resolution" means more image detail.
Image resolution can be measured in various ways. Resolution quantifies how ...
, the use of
outlines
Outline or outlining may refer to:
* Outline (list), a document summary, in hierarchical list format
* Code folding, a method of hiding or collapsing code or text to see content in outline form
* Outline drawing, a sketch depicting the outer edge ...
and how detailed the artwork is.
Image sensor capture binary images
Oversampled binary image sensor
An oversampled binary image sensor is an image sensor with non-linear response capabilities reminiscent of traditional photographic film. Each pixel in the sensor has a binary response, giving only a one-bit quantized measurement of the local light ...
is a new image sensor that is reminiscent of traditional photographic film. Each pixel in the sensor has a binary response, giving only a one-bit quantized measurement of the local light intensity.
See also
*
Black-and-white
Black-and-white (B&W or B/W) images combine black and white in a continuous spectrum, producing a range of shades of grey.
Media
The history of various visual media began with black and white, and as technology improved, altered to color. ...
*
Connected-component labeling Connected-component labeling (CCL), connected-component analysis (CCA), blob extraction, region labeling, blob discovery, or region extraction is an algorithmic application of graph theory, where subsets of connected components are uniquely labeled ...
*
Discrete tomography
Discrete tomography
Herman, G. T. and Kuba, A., Discrete Tomography: Foundations, Algorithms, and Applications, Birkhäuser Boston, 1999
Herman, G. T. and Kuba, A., Advances in Discrete Tomography and Its Applications, Birkhäuser Boston, 2007
fo ...
*
Netpbm format
Netpbm (formerly Pbmplus) is an open-source package of graphics programs and a programming library. It is used mainly in the Unix world, where one can find it included in all major open-source operating system distributions, but also works on Micr ...
*
JBIG
JBIG is an early lossless image compression standard from the Joint Bi-level Image Experts Group, standardized as ISO/IEC standard 11544 and as ITU-T recommendation T.82 in March 1993. It is widely implemented in fax machines. Now that the new ...
/
JBIG2
JBIG2 is an image compression standard for bi-level images, developed by the Joint Bi-level Image Experts Group. It is suitable for both lossless and lossy compression. According to a press release from the Group, in its lossless mode JBIG2 ty ...
*
X BitMap
In computer graphics, the X Window System used X BitMap (XBM), a plain text binary image format, for storing cursor and icon bitmaps used in the X GUI. The XBM format is superseded by XPM, which first appeared for X11 in 1989.
Format
XBM files ...
*
X PixMap
X PixMap (XPM) is an image file format used by the X Window System, created in 1989 by Daniel Dardailler and Colas Nahaboo working at Bull Research Center at Sophia Antipolis, France, and later enhanced by Arnaud Le Hors.
It is intended primaril ...
*
Oversampled binary image sensor
An oversampled binary image sensor is an image sensor with non-linear response capabilities reminiscent of traditional photographic film. Each pixel in the sensor has a binary response, giving only a one-bit quantized measurement of the local light ...
References
{{reflist
External links
Monochrome Bitmaps
1
Image processing
Digital geometry
2 (number)