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 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 ...

; 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 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 PGF (Progressive Graphics File) is a wavelet-based bitmapped image format that employs lossless and lossy data compression. PGF was created to improve upon and replace the JPEG format. It was developed at the same time as JPEG 2000 but with ...

image format, for instance.

Bitmap displays

Some computers displayed graphics in bit-plane format, most notably PC with EGA 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 A blitter is a circuit, sometimes as a coprocessor or a logic block on a microprocessor, dedicated to the rapid movement and modification of data within a computer's memory. A blitter can copy large quantities of data from one memory area to anot ...

chip), and parallax scrolling effects.

Video motion estimation

Some

motion estimation Motion estimation is the process of determining ''motion vectors'' that describe the transformation from one 2D image to another; usually from adjacent frames in a video sequence. It is an ill-posed problem as the motion is in three dimensions b ...

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 In computer programming, a bitwise operation operates on a bit string, a bit array or a binary numeral (considered as a bit string) at the level of its individual bits. It is a fast and simple action, basic to the higher-level arithmetic operati ...

and

popcount The Hamming weight of a string is the number of symbols that are different from the zero-symbol of the alphabet used. It is thus equivalent to the Hamming distance from the all-zero string of the same length. For the most typical case, a string ...

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 and synaptic state, SNNs incorporate the concept of time into their operating model. The idea is that neuro ...

, 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 In deep learning, a convolutional neural network (CNN, or ConvNet) is a class of artificial neural network (ANN), most commonly applied to analyze visual imagery. CNNs are also known as Shift Invariant or Space Invariant Artificial Neural Netwo ...

Programs

Many image processing packages can split an image into bit-planes. Open source tools such as Pamarith from

Netpbm 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 Mic ...

and Convert from

ImageMagick ImageMagick, invoked from the command line as magick, is a free and open-source cross-platform software suite for displaying, creating, converting, modifying, and editing raster images. Created in 1987 by John Cristy, it can read and write ove ...

can be used to generate bit-planes.

References

{{DEFAULTSORT:Bit Plane Bit data structures