zxing去白边

2025年了，可能干不了几年了，还能写这种文章还是有点可笑。

背景

zxing库生成的二维码自带白边

分析

生产二维码主要分两步：

1.用QRCodeWriter生成BitMatrix信息

2.根据信息生成bitmap

问题在1。

生成二维码的尺寸实际是有一些规格的，代码详细参见Encoder#encode，以下是具体规格：

确定输出变成的核心代码在QRCodeWriter#renderResult方法里，传入的边长和生成二维码的宽度可能不是倍数关系，比如传入边长15，但是二维码边长是7，那其实7*2=14就是最佳的最终二维码的边长了，剩余部分就是白边。知道了原因，解决方法如下，把输出尺寸变为二维码的倍数就好了。

解决

    private static BitMatrix renderResult(QRCode code, int width, int height, int quietZone) {ByteMatrix input = code.getMatrix();if (input == null) {throw new IllegalStateException();}int inputWidth = input.getWidth();int inputHeight = input.getHeight();int qrWidth = inputWidth + (quietZone * 2);int qrHeight = inputHeight + (quietZone * 2);int outputWidth = Math.max(width, qrWidth);int outputHeight = Math.max(height, qrHeight);int multiple = Math.min(outputWidth / qrWidth, outputHeight / qrHeight);// >> 去除白边 add by 某某outputWidth = qrWidth * multiple;outputHeight = qrHeight * multiple;// << 去除白边 add by 某某// Padding includes both the quiet zone and the extra white pixels to accommodate the requested// dimensions. For example, if input is 25x25 the QR will be 33x33 including the quiet zone.// If the requested size is 200x160, the multiple will be 4, for a QR of 132x132. These will// handle all the padding from 100x100 (the actual QR) up to 200x160.int leftPadding = (outputWidth - (inputWidth * multiple)) / 2;int topPadding = (outputHeight - (inputHeight * multiple)) / 2;BitMatrix output = new BitMatrix(outputWidth, outputHeight);for (int inputY = 0, outputY = topPadding; inputY < inputHeight; inputY++, outputY += multiple) {// Write the contents of this row of the barcodefor (int inputX = 0, outputX = leftPadding; inputX < inputWidth; inputX++, outputX += multiple) {if (input.get(inputX, inputY) == 1) {output.setRegion(outputX, outputY, multiple, multiple);}}}return output;}