1# PixelMap Operation (ArkTS) 2 3To process a certain area in an image, you can perform PixelMap operations, which are usually used to beautify the image. 4 5As shown in the figure below, the pixel data of a rectangle in an image is read, modified, and then written back to the corresponding area of the original image. 6 7**Figure 1** PixelMap operation 8 9 10 11## How to Develop 12 13Read [Image](../reference/apis-image-kit/js-apis-image.md#pixelmap7) for APIs related to PixelMap operations. 14 151. Complete [image decoding](image-decoding.md#how-to-develop) and obtain a **PixelMap** object. 16 172. Obtain information from the **PixelMap** object. 18 19 ```ts 20 import image from '@ohos.multimedia.image'; 21 // Obtain the total number of bytes of this PixelMap object. 22 let pixelBytesNumber : number = pixelMap.getPixelBytesNumber(); 23 // Obtain the number of bytes per row of this PixelMap object.p 24 let rowCount : number = pixelMap.getBytesNumberPerRow(); 25 // Obtain the pixel density of the image. Pixel density refers to the number of pixels per inch of an image. A larger value of the pixel density indicates a finer image. 26 let getDensity : number = pixelMap.getDensity(); 27 ``` 28 293. Read and modify the pixel data of the target area, and write the modified data back to the original image. 30 31 ```ts 32 import {BusinessError} from '@ohos.base' 33 // Scenario 1: Read the pixel data of the entire image and write the modified data to an array buffer. 34 const readBuffer = new ArrayBuffer(pixelBytesNumber); 35 pixelMap.readPixelsToBuffer(readBuffer).then(() => { 36 console.info('Succeeded in reading image pixel data.'); 37 }).catch((error : BusinessError) => { 38 console.error('Failed to read image pixel data. And the error is: ' + error); 39 }) 40 41 // Scenario 2: Read the pixel data in a specified area and write the modified data to area.pixels. 42 const area : image.PositionArea = { 43 pixels: new ArrayBuffer(8), 44 offset: 0, 45 stride: 8, 46 region: { size: { height: 1, width: 2 }, x: 0, y: 0 } 47 } 48 pixelMap.readPixels(area).then(() => { 49 console.info('Succeeded in reading the image data in the area.'); 50 }).catch((error : BusinessError) => { 51 console.error('Failed to read the image data in the area. And the error is: ' + error); 52 }) 53 54 // The read image data can be used independently (by creating a PixelMap object) or modified as required. 55 // Write area.pixels to the specified area. 56 pixelMap.writePixels(area).then(() => { 57 console.info('Succeeded to write pixelMap into the specified area.'); 58 }) 59 60 // Write the image data result to the PixelMap object. 61 const writeColor = new ArrayBuffer(96); 62 pixelMap.writeBufferToPixels(writeColor, () => {}); 63 ``` 64
