vision.IDCT System object

Package: vision

Compute 2-D inverse discrete cosine transform


The IDCT object computes 2-D inverse discrete cosine transform of the input signal. The number of rows and columns of the input matrix must be a power of 2.


H = vision.IDCT returns a System object, H, used to compute the two-dimensional inverse discrete cosine transform (2-D IDCT) of a real input signal.

H = vision.IDCT(Name,Value) returns a 2-D inverse discrete cosine transform System object, H, with each specified property set to the specified value. You can specify additional name-value pair arguments in any order as (Name1, Value1,...,NameN,ValueN).

Code Generation Support
Supports MATLAB® Function block: Yes
System Objects in MATLAB Code Generation.
Code Generation Support, Usage Notes, and Limitations.



Specify how the System object computes sines and cosines as Trigonometric function, or Table lookup. This property must be set to Table lookup for fixed-point inputs.

 Fixed-Point Properties


cloneCreate 2-D inverse discrete cosine transform object with same property values
getNumInputsNumber of expected inputs to step method
getNumOutputsNumber of outputs from step method
isLockedLocked status for input attributes and nontunable properties
release Allow property value and input characteristics changes
stepCompute 2-D inverse discrete cosine transform of the input


Use 2-D discrete cosine transform (DCT) to analyze the energy content in an image. Set the DCT coefficients lower than a threshold of 0. Reconstruct the image using 2-D inverse discrete cosine transform (IDCT).

 hdct2d = vision.DCT;
 I = double(imread('cameraman.tif'));
 J = step(hdct2d, I);
 imshow(log(abs(J)),[]), colormap(jet(64)), colorbar
 hidct2d = vision.IDCT;
 J(abs(J) < 10) = 0;
 It = step(hidct2d, J);
 figure, imshow(I, [0 255]), title('Original image')
 figure, imshow(It,[0 255]), title('Reconstructed image')


This object implements the algorithm, inputs, and outputs described on the 2-D IDCT block reference page. The object properties correspond to the block parameters.

See Also

Introduced in R2012a

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