Recognition APIs

Recognize Labels from Still Images

Recognize Labels from Video Frames

recognize

Recognizes labels from an image.

recognize(source: Blob | Buffer | ArrayBuffer | Uint8Array | Uint8ClampedArray | HTMLImageElement | HTMLCanvasElement | HTMLVideoElement | DCEFrame | string): Promise<DLRResult[]>

Parameters

source : specifies the image to recognize. The supported image formats include png , jpeg , bmp , gif and a few others (some browsers support webp , tif ). Also note that the image can be specified in a lot of ways including binary data, base64 string (with MIME), URL, etc.

Return value

A promise resolving to a DLRResult\[\] object that contains all the label results found in this image.

Code snippet

let results1 = await recognizer.recognize(blob);
let results2 = await recognizer.recognize(htmlImageElement);
let results3 = await recognizer.recognize(url);
let results4 = await recognizer.recognize(strBase64WithMime); // like `data:image/png;base64,iV************`

You can even use an HTMLVideoElement as the source. If the video is playing, the current frame will be recognized.

let results;
try {
    // The current frame will be recognized.
    results = await recognizer.recognize(htmlVideoElement);
    for (let result of results) {
        for (let lineResult of result.lineResults) {
            console.log(lineResult.text);
        }
    }
} catch (ex) {
    // If there is no frame in the video, throw an exception.   
}

See also

• Blob
• Buffer
• ArrayBuffer
• Uint8Array
• Uint8ClampedArray
• HTMLImageElement
• HTMLCanvasElement
• HTMLVideoElement
• DLRResult
• DCEFrame

recognizeBase64String

Recognizes labels from a base64-encoded image (with or without MIME).

recognizeBase64String(base64Str: string): Promise<DLRResult[]>

Parameters

base64Str : specifies the image represented by a string.

Return value

A promise resolving to a DLRResult\[\] object that contains all the label results found in this image.

Code snippet

let results = await recognizer.recognizeBase64String(strBase64); //e.g. `data:image/jpg;base64,Xfjshekk....` or `Xfjshekk...`.
for (let result of results) {
    for (let lineResult of result.lineResults) {
        console.log(lineResult.text);
    }
}

See also

• DLRResult

recognizeUrl

Recognizes labels from an image specified by its URL. Note that the image should either be from the same domain or has the ‘Access-Control-Allow-Origin’ header set to allow access from your current domain.

recognizeUrl(url: string): Promise<DLRResult[]>

Parameters

url : specifies the image by its URL.

Return value

A promise resolving to a DLRResult\[\] object that contains all the label results found in this image.

Code snippet

let results = await recognizer.recognizeUrl("https://www.yourdomain.com/imageWithBarcodes.png");
for (let result of results) {
    for (let lineResult of result.lineResults) {
        console.log(lineResult.text);
    }
}

See also

• DLRResult

recognizeBuffer

Recognizes labels from raw image data. It is an advanced API, if you don’t know what you are doing, use recognize instead.

recognizeBuffer(buffer: Blob | Buffer | ArrayBuffer | Uint8Array | Uint8ClampedArray, width: number, height: number, stride: number, format: EnumImagePixelFormat): Promise<DLRResult[]>

Parameters

buffer : specifies the raw image represented by a Uint8Array , Uint8ClampedArray , ArrayBuffer , Blob or Buffer object.

width: image width.

height: image height.

stride: image-width * pixel-byte-length.

format: pixel format.

Return value

A promise resolving to a DLRResult\[\] object that contains all the label results found in this image.

Code snippet

let results = await reader.recognizeBuffer(u8RawImage, 1280, 720, 1280 * 4, DLR.EnumDLRImagePixelFormat.IPF_ABGR_8888);
for (let result of results) {
    for (let lineResult of result.lineResults) {
        console.log(lineResult.text);
    }
}

See also

• Blob
• Buffer
• ArrayBuffer
• Uint8Array
• Uint8ClampedArray
• EnumImagePixelFormat
• DLRResult

onUniqueRead

This event is triggered when a new, unduplicated label is found.

onUniqueRead: (txt: string, results: DLRLineResult[]) => void

Arguments

txt : a string that holds the label text.

results : one or more DLRLineResult object(s) that contains more detailed info about the returned text.

Code Snippet

let recognizer = await Dynamsoft.DLR.LabelRecognizer.createInstance({
    runtimeSettings: "video-passportMRZ"
});
let enhancer = await Dynamsoft.DCE.CameraEnhancer.createInstance();
await enhancer.setUIElement(Dynamsoft.DLR.LabelRecognizer.defaultUIElementURL);
recognizer.cameraEnhancer = enhancer;
recognizer.onUniqueRead = (txt, results) => {
    console.log(txt);
}
recognizer.startScanning(true);

See also

• DLRLineResult

onFrameRead

This event is triggered after the library finishes scanning a frame.

onFrameRead: (results: DLRResult[]) => void

Arguments

results : a DLRResult object that contains all the label results in this frame.

Code Snippet

let recognizer = await Dynamsoft.DLR.LabelRecognizer.createInstance({
    runtimeSettings: "video-passportMRZ"
});
let enhancer = await Dynamsoft.DCE.CameraEnhancer.createInstance();
await enhancer.setUIElement(Dynamsoft.DLR.LabelRecognizer.defaultUIElementURL);
recognizer.cameraEnhancer = enhancer;
recognizer.onFrameRead = results => {
    for (let result of results) {
        for (let lineResult of result.lineResults) {
            console.log(lineResult.text);
        }
    }
};
recognizer.startScanning(true);

See also

• DLRResult

recognizeCurrentFrame

Scans the current frame of the video for barcodes.

recognizeCurrentFrame(): Promise<DLRResult[]>

Return value

A promise resolving to a DLRResult\[\] object that contains all the label results found in this frame.

Code Snippet

let recognizer = await Dynamsoft.DLR.LabelRecognizer.createInstance({
    runtimeSettings: "video-passportMRZ"
});
let enhancer = await Dynamsoft.DCE.CameraEnhancer.createInstance();
await enhancer.setUIElement(Dynamsoft.DLR.LabelRecognizer.defaultUIElementURL);
recognizer.cameraEnhancer = enhancer;
await cEnhancer.open();
let results = await recognizer.recognizeCurrentFrame();
for (let result of results) {
    for (let lineResult of result.lineResults) {
        console.log(lineResult.text);
    }
}

See also

• DLRResult

startScanning

Open the camera and starts continuous scanning of incoming frames.

startScanning(appendOrShowUI?: boolean): Promise<PlayCallbackInfo>;

Parameters

appendOrShowUI : this parameter specifies how to handle the UI that comes with the bound CameraEnhancer instance. When set to true, if the UI doesn’t exist in the DOM tree, the CameraEnhancer instance will append it in the DOM and show it; if the UI already exists in the DOM tree but is hidden, it’ll be displayed. When not set or set to false, it means not to change the original state of that UI: if it doesn’t exist in the DOM tree, nothing shows up on the page; if it exists in the DOM tree, it may or may not show up depending on its original state.

Return value

A promise resolving to a PlayCallbackInfo object which contains the resolution of the video.

Code Snippet

let recognizer = await Dynamsoft.DLR.LabelRecognizer.createInstance({
    runtimeSettings: "video-passportMRZ"
});
let enhancer = await Dynamsoft.DCE.CameraEnhancer.createInstance();
await enhancer.setUIElement(Dynamsoft.DLR.LabelRecognizer.defaultUIElementURL);
recognizer.cameraEnhancer = enhancer;
recognizer.onUniqueRead = (txt, results) => {
    console.log(txt);
    for (let result of results) {
        for (let lineResult of result.lineResults) {
            console.log(lineResult.text);
        }
    }
}
recognizer.startScanning(true);

See also

• DLRResult

pauseScanning

Pause continuous scanning but keep the video stream.

pauseScanning(): void;

resumeScanning

Resumes continuous scanning.

resumeScanning(): void;

stopScanning

Stops continuous scanning and closes the video stream.

stopScanning(hideUI?: boolean): void;

Parameters

hideUI : this parameter specifies how to handle the UI that comes with the bound CameraEnhancer instance. When set to true, if the UI doesn’t exist in the DOM tree or it exists but is hidden, nothing is done; if the UI already exists in the DOM tree and is shown, it’ll be hidden. When not set or set to false, it means not to change the original state of that UI: if it doesn’t exist in the DOM tree, nothing happens; if it exists in the DOM tree, it may or may not be hidden depending on its original state.

Code Snippet

let recognizer = await Dynamsoft.DLR.LabelRecognizer.createInstance({
    runtimeSettings: "video-passportMRZ"
});
let enhancer = await Dynamsoft.DCE.CameraEnhancer.createInstance();
await enhancer.setUIElement(Dynamsoft.DLR.LabelRecognizer.defaultUIElementURL);
recognizer.cameraEnhancer = enhancer;
recognizer.onUniqueRead = (txt, results) => {
    console.log(txt);
    for (let result of results) {
        for (let lineResult of result.lineResults) {
            console.log(lineResult.text);
        }
    }
    // Stops scanning the video input as soon as a label is found.
    recognizer.stopScanning(true);
}
await recognizer.startScanning(true);

See also

• DLRResult