Android zxing – portrait camera preview/surfaceview is stretched/warped

Android ZXing: Portrait Camera Preview/SurfaceView Stretched/Warped

This article addresses a common issue encountered when using ZXing library in Android for barcode scanning – the camera preview in portrait mode appearing stretched or warped.

Understanding the Issue

The problem stems from the discrepancy between the aspect ratios of the camera sensor and the display. Typically, camera sensors have a 4:3 aspect ratio, while displays usually have a 16:9 ratio. When using a SurfaceView (the default view for displaying the camera preview) in portrait mode, Android attempts to fit the camera’s 4:3 output into the 16:9 display, resulting in distortion.

Solutions

1. Aspect Ratio Correction

The most common solution involves manually adjusting the SurfaceView’s dimensions to match the camera preview’s aspect ratio. This ensures that the preview is displayed without any distortion.

Code Example:

// Get the camera preview size
Camera.Size previewSize = camera.getParameters().getPreviewSize();

// Calculate the aspect ratio
float aspectRatio = (float) previewSize.width / previewSize.height;

// Adjust the SurfaceView's dimensions to match the aspect ratio
int surfaceWidth = surfaceView.getWidth();
int surfaceHeight = (int) (surfaceWidth / aspectRatio);
surfaceView.getLayoutParams().height = surfaceHeight;
surfaceView.requestLayout();

2. Custom Preview Renderer

Alternatively, you can avoid using SurfaceView altogether and implement a custom preview renderer using OpenGL ES or other rendering techniques. This provides more control over the preview’s rendering process and eliminates the need for manual aspect ratio correction.

3. Using a Different Camera

If you have access to multiple cameras, you might be able to choose one with an aspect ratio that matches your display. This approach avoids the distortion issue altogether, but might not always be feasible.

Choosing the Best Solution

Additional Tips

• Ensure that the camera is correctly configured with the desired preview size.
• Consider using a third-party library like Zxing’s built-in camera configuration utility to simplify camera setup.
• Test your application on different devices with varying display aspect ratios to ensure compatibility.