Function Description

Functions

The following tables Table 1 and Table 2 describe the functions of the vision preprocessing core (VPC) and the function support of each version.

APIs described in this section are asynchronous APIs. The API call delivers a task rather than executes a task. After this API is called, call the synchronization API (for example, acl.rt.synchronize_stream) to ensure that the task is complete.

**Table 1** Introduction
Functionality	Description
Cropping	Crops one or more selected regions of interest (ROIs) from one or more images.
Resizing	8K resizing and non-8K resizing are supported for images based on resolutions. Resizes an ROI (supporting uncompressed format) or multiple ROIs from a single image (supporting uncompressed format). Supports other resizing modes, such as resizing an image without cropping it and resizing an image with the aspect ratio preserved.
Overlaying	Crops an image out of an input image, resizes the cropped image, and places it in a specified area of the output image. The output image may be a blank image (when the output buffer allocated by the user is empty) or an existing image (when an image has been read into the output buffer allocated by the user). Note that the overlaying concept here refers only to the case when the output image is an existing image.
Stitching	Crops selected ROIs from the input image, resizes the cropped images, and loads them to specified areas in the output buffer.
Image pyramid	Successively downsamples an image using a Gaussian filter.
Histogram analysis	Collects statistics on the pixel value distribution of each image channel (RGB/YUV).
Remapping	Remaps an image to a new one based on the given configuration.
Border making	Creates a border around an image (also referred to as padding).
Format conversion	Converts between RGB and YUV.
Image grayscale	Converts a color image into a grayscale image. Note that grayscale input images produce only grayscale output images.

**Table 2** Supported product functions
Function	Atlas 200/300/500 Inference Product	Atlas Training Series Product
Cropping	√	√
Resizing	√	√
Pasting	√	√
Stitching	√	√
Image pyramid	x	x
Histogram analysis	x	x
Remapping	x	x
Border making	x	x
Format conversion	√	√
Image grayscale	√ Only the data of the Y component is extracted from the YUV420SP output image.	√ Only the data of the Y component is extracted from the YUV420SP output image.

Function Diagrams (Atlas 200/300/500 Inference Product) (Atlas Training Series Product)

Figure 1 VPC function diagram (cropping+resizing+pasting)

Figure 2 VPC function diagram (stitching)

Figure 3 Resizing with the aspect ratio preserved (paste ROI centered on the output image)

Figure 4 Resizing with the aspect ratio preserved (paste ROI vertically centered on the output image)

Figure 5 Resizing with the aspect ratio preserved (paste ROI horizontally centered on the output image)

Reference

The following figure shows the component layout of the RGB and YUV formats. Two YUV420SP images are used as examples for the semi-planar format and an ARGB image is used as an example for the Packed and RGB formats.

Parent topic: VPC