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This article introduces how to use Opencv to transform the identity card of trinket. The content is very detailed. Interested friends can use it for reference. I hope it will be helpful to you.

Sometimes we need ID card identification on the project, but the ID cards taken by some people are either upside down or crooked. It is troublesome to let the background identify it, and it is often incorrectly identified. But with the perspective transformation of opencv, no matter how crooked you are, I can help you correct it.

The principle of perspective transformation

Perspective transformation (Perspective Transformation) is the projection of an image onto a new view plane (Viewing Plane), also known as projection mapping (Projective Mapping). As shown in the figure

JAVA implementation

First of all, get the coordinates of the four points of the ID card. Https://uutool.cn/img-coord/ this website can obtain the picture coordinates online. In fact, during the project, the coordinates of these four points can be transmitted to you by the front end.

Import org.opencv.core.*;import org.opencv.imgcodecs.Imgcodecs;import org.opencv.imgproc.Imgproc;import org.opencv.utils.Converters;import java.util.List;public class PerspectiveTransform {public static void main (String [] args) {String srcImgPath = "/ home/IdeaProjects/opencv-java/src/main/resources/2020-09-13,11-55.png"; String x1 = "104278"; String x2 = "523,49"; String x3 = "652235" String x4 = "223491"; String destImgPath = "/ home/IdeaProjects/opencv-java/src/main/resources/test5.png"; perspectiveTransform (srcImgPath,x1,x2,x3,x4,destImgPath);} private static void perspectiveTransform (String srcImgPath,String x1, String x2, String x3 dint string x4, String destImgPath) {System.loadLibrary (Core.NATIVE_LIBRARY_NAME) Mat src = Imgcodecs.imread (srcImgPath); / / read the image into the matrix and take the grayscale image if (src.empty ()) {return;} try {Mat dst = new Mat (); List listSrcs = java.util.Arrays.asList (getPoint (x1), getPoint (x2), getPoint (x3), getPoint (x4)) Mat srcPoints = Converters.vector_Point_to_Mat (listSrcs, CvType.CV_32F); List listDsts = java.util.Arrays.asList (new Point (0,0), new Point (1011, 0), new Point (1011), new Point (0638); Mat dstPoints = Converters.vector_Point_to_Mat (listDsts, CvType.CV_32F) Mat perspectiveMmat = Imgproc.getPerspectiveTransform (srcPoints, dstPoints); Size size = new Size (new Point (1011)); Imgproc.warpPerspective (src, dst, perspectiveMmat, size, Imgproc.INTER_LINEAR); Mat gray = gray (dst); Imgcodecs.imwrite (destImgPath, gray);} catch (Exception e) {e.printStackTrace () }} private static Point getPoint (String points) {if (points = = null | | ".equals (points)) {throw new NullPointerException (" coordinate parameter is empty ");} String [] split = points.split (", "); if (split.length = = 0) {throw new NullPointerException (" coordinate parameter is empty ") } return new Point (Double.valueOf (split [0]), Double.valueOf (split [1]));} / * function: ashing * * @ param src Mat matrix image * @ return * / public static Mat gray (Mat src) {Mat gray = new Mat () If (src.channels () = = 3) {Imgproc.cvtColor (src, gray, Imgproc.COLOR_BGR2GRAY); src = gray;} else {System.out.println ("The Image File Is Not The RGB File!");} return src }} on how to use Opencv to trinket ID card perspective transformation to share here, I hope the above content can be of some help to you, can learn more knowledge. If you think the article is good, you can share it for more people to see.

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