Android Zxing 转换竖屏扫描且提高识别率的方法

作者：袖梨 2022-06-25

最近的一个Android需要用到扫码功能，用的是Zxing开源库。Zxing的集成就不说了，但是Zxing默认的是横屏扫码，在实际生产中并不适用，需要改为竖屏扫描。

转竖屏步骤：

1>. AndroidManifest.xml中把activity标签CaptureActivity部分的screenOrientation改为portrait。

android:screenOrientation="portrait"

2>. CameraManager类中的getFramingRectInPreview()方法，将left， right， top， bottom改变。

//竖屏
rect.left = rect.left * cameraResolution.y / screenResolution.x;
rect.right = rect.right * cameraResolution.y / screenResolution.x;
rect.top = rect.top * cameraResolution.x / screenResolution.y;
rect.bottom = rect.bottom * cameraResolution.x / screenResolution.y;

3>. CameraConfigurationManager类中的setDesiredCameraParameters(OpenCamera camera, boolean safeMode)方法，在setParameters之前添加

theCamera.setDisplayOrientation(90);

4>. DecodeHandler类中的decode(byte[] data, int width, int height)方法，在PlanarYUVLuminanceSource source = activity.getCameraManager().buildLuminanceSource(data, width, height)之前添加

byte[] rotatedData = new byte[data.length];
for (int y = 0; y < height; y++) {
for (int x = 0; x < width; x++)
  rotatedData[x * height + height - y - 1] = data[x + y * width];
}
int tmp = width; // Here we are swapping, that's the difference to #11
width = height;
height = tmp;
data = rotatedData;

此时，竖屏扫描已经可以实现了，但是扫描复杂的图码时，分辨率低的已经分不清纹理了，很难识别出来，所以需要优化识别率。

识别率优化：

1>. CameraConfigurationUtils类中的findBestPreviewSizeValue(Camera.Parameters parameters, Point screenResolution)方法，将double screenAspectRatio = screenResolution.x / (double) screenResolution.y改为

double screenAspectRatio;
if (screenResolution.x > screenResolution.y) {
  screenAspectRatio = (double) screenResolution.x / (double) screenResolution.y;
} else {
  screenAspectRatio = (double) screenResolution.y / (double) screenResolution.x;
}

2>. 至此，识别率已经很大程度上的提高了，若在要提高识别率，可通过修改CameraManager类中的MAX_FRAME_WIDTH和MAX_FRAME_HEIGHT来提高精度。