![Lichtenstein bitplanes](https://upload.wikimedia.org/wikipedia/commons/4/48/Lichtenstein_bitplanes.png)
A bit plane of a
digital
Digital usually refers to something using discrete digits, often binary digits.
Technology and computing Hardware
*Digital electronics, electronic circuits which operate using digital signals
**Digital camera, which captures and stores digital i ...
discrete signal
In Dynamical system, mathematical dynamics, discrete time and continuous time are two alternative frameworks within which Variable (mathematics), variables that evolve over time are modeled.
Discrete time
Discrete time views values of variable ...
(such as image or sound) is a set of
bit
The bit is the most basic unit of information in computing and digital communications. The name is a portmanteau of binary digit. The bit represents a logical state with one of two possible values. These values are most commonly represente ...
s corresponding to a given bit position in each of the
binary number
A binary number is a number expressed in the base-2 numeral system or binary numeral system, a method of mathematical expression which uses only two symbols: typically "0" (zero) and "1" ( one).
The base-2 numeral system is a positional notatio ...
s representing the signal.
For example, for
16-bit
16-bit microcomputers are microcomputers that use 16-bit microprocessors.
A 16-bit register can store 216 different values. The range of integer values that can be stored in 16 bits depends on the integer representation used. With the two mos ...
data representation there are 16 bit planes: the first bit plane contains the set of the most significant bit, and the 16th contains the least significant bit.
It is possible to see that the first bit plane gives the roughest but the most critical approximation of values of a medium, and the higher the number of the bit plane, the less is its contribution to the final stage. Thus, adding a bit plane gives a better approximation.
If a bit on the nth bit plane on an m-bit dataset is set to 1, it contributes a value of 2
m−n, otherwise it contributes nothing. Therefore, bit planes can contribute half of the value of the previous bit plane. For example, in the 8-bit value 10110101 (181 in decimal) the bit planes work as follows:
Bit plane is sometimes used as synonymous to
Bitmap; however, technically the former refers to the location of the data in memory and the latter to the data itself.
One aspect of using bit-planes is determining whether a bit-plane is random noise or contains significant information.
One method for calculating this is to compare each pixel to three adjacent pixels , and . If the pixel is the same as at least two of the three adjacent pixels, it is not noise. A noisy bit-plane will have 49% to 51% pixels that are noise.
Applications
Media file formats
As an example, in
PCM
Pulse-code modulation (PCM) is a method used to digitally represent sampled analog signals. It is the standard form of digital audio in computers, compact discs, digital telephony and other digital audio applications. In a PCM stream, the amp ...
sound
encoding
In communications and information processing, code is a system of rules to convert information—such as a letter, word, sound, image, or gesture—into another form, sometimes shortened or secret, for communication through a communication ...
the first bit in the sample denotes the sign of the function, or in other words defines the half of the whole
amplitude
The amplitude of a periodic variable is a measure of its change in a single period (such as time or spatial period). The amplitude of a non-periodic signal is its magnitude compared with a reference value. There are various definitions of amplit ...
values range, and the last bit defines the precise value. Replacement of more significant bits result in more distortion than replacement of less significant bits. In lossy
media compression that uses bit-planes it gives more freedom to encode less significant bit-planes and it is more critical to preserve the more significant ones.
As illustrated in the image above, the early bitplanes, particularly the first, may have constant runs of bits, and thus can be efficiently encoded by
run-length encoding
Run-length encoding (RLE) is a form of lossless data compression in which ''runs'' of data (sequences in which the same data value occurs in many consecutive data elements) are stored as a single data value and count, rather than as the original ...
. This is done (in the transform domain) in the
Progressive Graphics File image format, for instance.
Bitmap displays
Some computers displayed graphics in
bit-plane format, most notably PC with
EGA
Ega or EGA may refer to:
Military
* East German Army, the common western name for the National People's Army
* Eagle, Globe, and Anchor, the emblem of the United States Marine Corps
People
* Aega (mayor of the palace), 7th-century noble of Neus ...
graphics card, the
Amiga
Amiga is a family of personal computers introduced by Commodore in 1985. The original model is one of a number of mid-1980s computers with 16- or 32-bit processors, 256 KB or more of RAM, mouse-based GUIs, and significantly improved graphi ...
and
Atari ST
The Atari ST is a line of personal computers from Atari Corporation and the successor to the Atari 8-bit family. The initial model, the Atari 520ST, had limited release in April–June 1985 and was widely available in July. It was the first pers ...
, contrasting with the more common
packed format. This allowed certain classes of image manipulation to be performed using bitwise operations (especially by a
blitter chip), and parallax scrolling effects.
Video motion estimation
Some
motion estimation algorithms can be performed using bit planes (e.g. after the application of a filter to turn salient edge features into binary values). This can sometimes provide a good enough approximation for correlation operations with minimal computational cost. This relies on an observation that the spatial information is more significant than the actual values. Convolutions may be reduced to
bit shift and
popcount operations, or performed in dedicated hardware.
Neural nets
Bitplane formats may be used for passing images to
Spiking neural networks
Spiking neural networks (SNNs) are artificial neural networks that more closely mimic natural neural networks. In addition to neuronal
A neuron, neurone, or nerve cell is an electrically excitable cell that communicates with other cells vi ...
, or low precision approximations to
neural networks
A neural network is a network or circuit of biological neurons, or, in a modern sense, an artificial neural network, composed of artificial neurons or nodes. Thus, a neural network is either a biological neural network, made up of biological ...
/
convolutional neural networks.
Programs
Many image processing packages can split an image into bit-planes. Open source tools such as Pamarith from
Netpbm and Convert from
ImageMagick can be used to generate bit-planes.
See also
*
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, or the number of bits used for each color component of a single pixel. When referring to ...
*
Planar
*
Binary image
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 ''1b ...
References
{{DEFAULTSORT:Bit Plane
Bit data structures