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# MLImageConstraint

The width, height, and pixel format constraints of an image feature.

```
class MLImageConstraint
```

## Overview

In CoreML, an *image* is a collection of pixels represented by <doc://com.apple.documentation/documentation/CoreVideo/cvpixelbuffer-q2e> (Swift) or <doc://com.apple.documentation/documentation/CoreVideo/CVPixelBuffer> (Objective-C). An *image feature* is a model input or output that accepts or produces, respectively, an image bundled in an [`MLFeatureValue`](/documentation/CoreML/MLFeatureValue). `MLImageConstraint` defines the image feature’s limitations for the images within an `MLFeatureValue`.

If a model has an image feature for an input or output, the model author uses an *image feature description* by creating an [`MLFeatureDescription`](/documentation/CoreML/MLFeatureDescription). The feature description for an image input or output has:

- Its [`type`](/documentation/CoreML/MLFeatureDescription/type) property set to [`MLFeatureType.image`](/documentation/CoreML/MLFeatureType/image)
- Its [`imageConstraint`](/documentation/CoreML/MLFeatureDescription/imageConstraint) property set to an [`MLImageConstraint`](/documentation/CoreML/MLImageConstraint) instance configured to the image feature’s size and format

Image features that support additional image sizes provide a range of sizes, or a list of discrete sizes, in their image constraint’s [`sizeConstraint`](/documentation/CoreML/MLImageConstraint/sizeConstraint) property.

## Topics

### Accessing the constraints

[`pixelsWide`](/documentation/CoreML/MLImageConstraint/pixelsWide)

The model’s default width for an image feature.

[`pixelsHigh`](/documentation/CoreML/MLImageConstraint/pixelsHigh)

The model’s default height for an image feature.

[`pixelFormatType`](/documentation/CoreML/MLImageConstraint/pixelFormatType)

The model’s pixel format for an image feature.

### Inspecting acceptable sizes

[`sizeConstraint`](/documentation/CoreML/MLImageConstraint/sizeConstraint)

Additional sizes this image feature supports.

[`MLImageSizeConstraint`](/documentation/CoreML/MLImageSizeConstraint)

A list or range of sizes that augment an image constraint’s default size.


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