Read block of big image



data = getBlock(bigimg,level,locationWorld) reads the big image data in bigimg at the specified resolution level, and returns pixel data for the entire block that contains coordinate locationWorld.


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Create a bigimage using a modified version of image "tumor_091.tif" from the CAMELYON16 data set. The original image is a training image of a lymph node containing tumor tissue. The original image has eight resolution levels, and the finest level has resolution 53760-by-61440. The modified image has only three coarse resolution levels. The spatial referencing of the modified image has been adjusted to enforce a consistent aspect ratio and to register features at each level.

bim = bigimage('tumor_091R.tif');

Display the bigimage by using the bigimageshow function. Overlay a grid that shows the block boundaries at the finest resolution level.

hb = subplot(1,2,1);

Specify the (x,y) coordinate of a block to display. Get the block containing the coordinate. Add a Point ROI over the displayed bigimage at the specified coordinate.

coord = [2500,2500];
blk = getBlock(bim,1,coord);
hp = drawpoint(hb,'Position',coord);

In the figure, display the block next to the entire bigimage. You can use imshow to display the block because the block fits in memory and has a single resolution level.

ha = subplot(1,2,2);

Add a listener to the Point ROI. When you drag the ROI with the mouse, the figure is updated to show the block containing the current ROI coordinates.

title(hb,'Drag Point to Select Block');
addlistener(hp, ...
    'ROIMoved',@(~,~) imshow(getBlock(bim,1,hp.Position),'Parent',ha));

Input Arguments

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Big image, specified as a bigimage object.

Resolution level, specified as a positive integer that is less than or equal to the number of resolution levels of bigimg.

Coordinate of a point, specified as a 1-by-2 numeric vector of the form [x y]. The location is specified in world coordinates, which are the pixel locations relative to the highest resolution level. The position must be a valid position within bigimg.

Output Arguments

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Pixel data, returned as a numeric array of the same data type as the big image, bigimg.ClassUnderlying.

Introduced in R2019b