# blocksub2sub

Convert block subscripts to pixel subscripts

Since R2021a

## Description

example

[pStart,pEnd] = blocksub2sub(bim,blocksub) converts a block subscript to pixel subscripts. pStart is the pixel subscripts of the first pixel in the block. pEnd is the pixel subscripts of the last pixel in the block. Note: For partial blocks pEnd represents the last valid pixel subscript in the image.

[pStart,pEnd] = blocksub2sub(bim,blocksub,'Level',L) additionally specifies the resolution level to use in a multiresolution image. Level defaults to 1.

## Examples

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Create a small sample image as a 5-by-7 matrix of zeros. Here is an illustration of the small sample image, with the pixel coordinates of the four corners provided.

Create a blocked image from the sample image, specifying a 2-by-2 block size. To create this blocked image, use blockedImage in write mode.

bim = blockedImage([],[5 7],[2 2],uint8(0),"Mode",'w');

Here is an illustration of the blocked image overlaid on the original image. It is divided into 2-by-2 blocks. In the diagram, each block contains its block coordinates.

Convert block subscripts into pixel subscripts by using the blocksub2sub function. By default, if the image is a multiresolution image, blocksub2sub uses pixel coordinates from coarsest level, although you can specify any level. Since the sample image has only one resolution level, blocksub2sub converts level 1.

[pstart,pend] = blocksub2sub(bim,[2 3])
pstart = 1×2

3     5

pend = 1×2

4     6

This illustration show the block coordinate [2 3] converted to pixel coordinates.

## Input Arguments

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Blocked image, specified as a blockedImage object.

Block subscripts, specified as a numeric array of positive integers.

Example: [2 3]

## Output Arguments

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Subscript of first pixel in the specified block, returned as a numeric array.

Subscript of last pixel in the specified block, returned as a numeric array.

## Version History

Introduced in R2021a