intlut

Convert integer values using lookup table

Syntax

B = intlut(A,lut)

Description

B = intlut(A,lut) converts values in array A based on lookup table lut and returns these new values in array B.

Examples

Convert Integer Values Using Lookup Table

Create an array of integers.

A = uint8([1 2 3 4; 5 6 7 8; 9 10 0 1])

A = 3×4 uint8 matrix

    1    2    3    4
    5    6    7    8
    9   10    0    1

Create a lookup table. In this example, the lookup table is created by following the vector [2 4 8 16] with repeated copies of the vector [0 150 200 250].

LUT = [2 4 8 16 repmat(uint8([0 150 200 255]),1,63)];

Convert the values of A by referring to the lookup table. Note that the first index of the lookup table is 0.

B = intlut(A, LUT)

B = 3×4 uint8 matrix

     4     8    16     0
   150   200   255     0
   150   200     2     4

Input Arguments

A — Input matrix

array of integers

Input matrix, specified as an array of integers.

Data Types: int16 | uint8 | uint16

lut — Lookup table

vector of integers

Lookup table, specified as a vector of integers.

• If A has data type uint8, then lut must be a uint8 vector with 256 elements.

• If A has data type uint16 or int16, then lut must be a vector with 65536 elements of the same class as A.

Data Types: int16 | uint8 | uint16

Output Arguments

B — Converted matrix

array of integers

Converted matrix, returned as an array of integers. B has the same size and data type as A.

Data Types: int16 | uint8 | uint16

Algorithms

• When A has data type uint8 or uint16, an offset of 1 is applied when indexing into the lookup table. For example, if an element of A has the value alpha, then the corresponding element in B has the value lut(alpha+1).

• When A has data type int16, an additional offset of 32768 is applied to the lookup table index. For example, if an element of A has the value alpha, then the corresponding element in B has the value lut(alpha+32768+1).

Extended Capabilities

C/C++ Code Generation

Generate C and C++ code using MATLAB® Coder™.

Usage notes and limitations:

• intlut supports the generation of C code (requires MATLAB^® Coder™). Note that if you choose the generic MATLAB Host Computer target platform, intlut generates code that uses a precompiled, platform-specific shared library. Use of a shared library preserves performance optimizations but limits the target platforms for which code can be generated. For more information, see Types of Code Generation Support in Image Processing Toolbox.

GPU Code Generation
Generate CUDA® code for NVIDIA® GPUs using GPU Coder™.

Thread-Based Environment

Run code in the background using MATLAB® backgroundPool or accelerate code with Parallel Computing Toolbox™ ThreadPool.

This function fully supports thread-based environments. For more information, see Run MATLAB Functions in Thread-Based Environment.

Version History

Introduced before R2006a

R2022b: Support for thread-based environments

intlut now supports thread-based environments.