application-dev/media/image.md

# Image Development

## When to Use

You can use image development APIs to decode images into pixel maps and encode the pixel maps into a supported format.

## Available APIs

For details about the APIs, see [Image Processing](../reference/apis/js-apis-image.md).

## How to Develop

### Full-Process Scenario

The full process includes creating an instance, reading image information, reading and writing pixel maps, updating data, packaging pixels, and releasing resources.

```js
const color = new ArrayBuffer(96); // Create a buffer to store image pixel data.
let opts = { alphaType: 0, editable: true, pixelFormat: 4, scaleMode: 1, size: { height: 2, width: 3 } } // Image pixel data.

// Create a PixelMap object.
image.createPixelMap(color, opts, (err, pixelmap) => {
    console.log('Succeeded in creating pixelmap.');
    // Failed to create the PixelMap object.
    if (err) {
        console.info('create pixelmap failed, err' + err);
        return
    }

    // Read pixels.
    const area = {
        pixels: new ArrayBuffer(8),
        offset: 0,
        stride: 8,
        region: { size: { height: 1, width: 2 }, x: 0, y: 0 }
    }
    pixelmap.readPixels(area,() => {
        let bufferArr = new Uint8Array(area.pixels);
        let res = true;
        for (let i = 0; i < bufferArr.length; i++) {
            console.info(' buffer ' + bufferArr[i]);
            if(res) {
                if(bufferArr[i] == 0) {
                    res = false;
                    console.log('readPixels end.');
                    break;
                }
            }
        }
    })

    // Store pixels.
    const readBuffer = new ArrayBuffer(96);
    pixelmap.readPixelsToBuffer(readBuffer,() => {
        let bufferArr = new Uint8Array(readBuffer);
        let res = true;
        for (let i = 0; i < bufferArr.length; i++) {
            if(res) {
                if (bufferArr[i] !== 0) {
                    res = false;
                    console.log('readPixelsToBuffer end.');
                    break;
                }
            }
        }
    })

    // Write pixels.
    pixelmap.writePixels(area,() => {
        const readArea = { pixels: new ArrayBuffer(20), offset: 0, stride: 8, region: { size: { height: 1, width: 2 }, x: 0, y: 0 }}
        pixelmap.readPixels(readArea,() => {
            let readArr = new Uint8Array(readArea.pixels);
            let res = true;
            for (let i = 0; i < readArr.length; i++) {
                if(res) {
                    if (readArr[i] !== 0) {
                        res = false;
                        console.log('readPixels end.please check buffer');
                        break;
                    }
                }
            }
        })
    })

    const writeColor = new ArrayBuffer(96); // Pixel data of the image.
    // Write pixels to the buffer.
    pixelmap.writeBufferToPixels(writeColor).then(() => {
        const readBuffer = new ArrayBuffer(96);
        pixelmap.readPixelsToBuffer(readBuffer).then (() => {
            let bufferArr = new Uint8Array(readBuffer);
            let res = true;
            for (let i = 0; i < bufferArr.length; i++) {
                if(res) {
                    if (bufferArr[i] !== i) {
                        res = false;
                        console.log('readPixels end.please check buffer');
                        break;
                    }
                }
            }
        })
    })

    // Obtain image information.
    pixelmap.getImageInfo((err, imageInfo) => {
        // Failed to obtain the image information.
        if (err || imageInfo == null) {
            console.info('getImageInfo failed, err' + err);
            return
        }
        if (imageInfo !== null) {
            console.log('Succeeded in getting imageInfo');
        }
    })

    // Release the PixelMap object.
    pixelmap.release(()=>{
        console.log('Succeeded in releasing pixelmap');
    })
})

// Create an image source (uri).
let path = '/data/local/tmp/test.jpg';
const imageSourceApi1 = image.createImageSource(path);

// Create an image source (fd).
let fd = 29;
const imageSourceApi2 = image.createImageSource(fd);

// Create an image source (data).
const data = new ArrayBuffer(96);
const imageSourceApi3 = image.createImageSource(data);

// Release the image source.
imageSourceApi3.release(() => {
    console.log('Succeeded in releasing imagesource');
})

// Encode the image.
const imagePackerApi = image.createImagePacker();
const imageSourceApi = image.createImageSource(0);
let packOpts = { format:"image/jpeg", quality:98 };
imagePackerApi.packing(imageSourceApi, packOpts, (err, data) => {
    if (err) {
        console.info('packing from imagePackerApi failed, err' + err);
        return
    }
    console.log('Succeeded in packing');
})

// Release the ImagePacker object.
imagePackerApi.release();
```

### Decoding Scenario

```js
let path = '/data/local/tmp/test.jpg'; // Set the path for creating an image source.

// Create an image source using a path.
const imageSourceApi = image.createImageSource(path); // '/data/local/tmp/test.jpg'

// Set parameters.
let decodingOptions = {
    sampleSize:1, // Sampling size of the thumbnail.
    editable: true, // Whether the image can be edited.
    desiredSize:{ width:1, height:2}, // Desired output size of the image.
    rotateDegrees:10, // Rotation angle of the image.
    desiredPixelFormat:2, // Decoded pixel format.
    desiredRegion: { size: { height: 1, width: 2 }, x: 0, y: 0 }, // Region of the image to decode.
    index:0// Image sequence number.
    };

// Create a pixel map in callback mode.
imageSourceApi.createPixelMap(decodingOptions, (err, pixelmap) => {
    // Failed to create the PixelMap object.
    if (err) {
        console.info('create pixelmap failed, err' + err);
        return
    }
    console.log('Succeeded in creating pixelmap.');
})

// Create a pixel map in promise mode.
imageSourceApi.createPixelMap().then(pixelmap => {
    console.log('Succeeded in creating pixelmap.');

    // Obtain the number of bytes in each line of pixels.
    let num = pixelmap.getBytesNumberPerRow();

    // Obtain the total number of pixel bytes.
    let pixelSize = pixelmap.getPixelBytesNumber();

    // Obtain the pixel map information.
    pixelmap.getImageInfo().then( imageInfo => {});

    // Release the PixelMap object.
    pixelmap.release(()=>{
        console.log('Succeeded in releasing pixelmap');
    })
}).catch(error => {
    console.log('Failed in creating pixelmap.' + error);
})
```

### Encoding Scenario

```js
let path = '/data/local/tmp/test.png' // Set the path for creating an image source.

// Set the image source.
const imageSourceApi = image.createImageSource(path); // '/data/local/tmp/test.png'

// Print the error message if the image source fails to be created.
if (imageSourceApi == null) {
    console.log('Failed in creating imageSource.');
}

// Create an image packer if the image source is successfully created.
const imagePackerApi = image.createImagePacker();

// Print the error information if the image packer fails to be created.
if (imagePackerApi == null) {
    console.log('Failed in creating imagePacker.');
}

// Set encoding parameters if the image packer is successfully created.
let packOpts = { format:"image/jpeg", // The supported encoding format is jpg.
                 quality:98 } // Image quality, which ranges from 0 to 100.

// Encode the image.
imagePackerApi.packing(imageSourceApi, packOpts)
.then( data => {
    console.log('Succeeded in packing');
})

// Release the image packer after the encoding is complete.
imagePackerApi.release();

// Obtain the image source information.
imageSourceApi.getImageInfo((err, imageInfo) => {
    console.log('Succeeded in getting imageInfo');
})

const array = new ArrayBuffer(100); // Incremental data.
// Update incremental data.
imageSourceApi.updateData(array, false, 0, 10,(error, data)=> {})

```

### Using ImageReceiver

Example scenario: The camera functions as the client to transmit image data to the server.

```js
public async init(surfaceId: any) {

    // (Server code) Create an ImageReceiver object.
    let receiver = image.createImageReceiver(8 * 1024, 8, image.ImageFormat.JPEG, 1);

    // Obtain the surface ID.
    receiver.getReceivingSurfaceId((err, surfaceId) => {
    // Failed to obtain the surface ID.
        if (err) {
            console.info('getReceivingSurfaceId failed, err' + err);
            return
        }
        console.info("receiver getReceivingSurfaceId success");
    });
    // Register a surface listener, which is triggered after the buffer of the surface is ready.
    receiver.on('imageArrival', () => {
        // Obtain the latest buffer of the surface.
        receiver.readNextImage((err, img) => {
            img.getComponent(4, (err, component) => {
                // Consume component.byteBuffer. For example, save the content in the buffer as an image.
		    })
	    })
    })

    // Call a Camera API to transfer the surface ID to the camera, which then obtains the surface based on the surface ID and generates a surface buffer.
}
```