Java图片比对

 在自动化测试中，除了普通的值验证，经常还有一些图片验证，比如图片的匹配率，输出图片的差异图片等。本文主要用到了BufferedImage类来操作图片比对和输出差异图片，大体的思路如下：

1. 通过ImageIO读入图片，生成相应的BufferedImage实例（Image操作流）

2. 修改目标图片的尺寸大小，以适应期望图片的大小（为像素比对做准备）

3. 获取每一个（width，height）的ARGB，并获取相应的Red, Green,Blue的值

4. 按照每个像素点的R,G,B进行比较（需要定义允许的R,G,B的误差）

5. 统计不同的像素点，生成diff图片

 

代码如下：

 

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import javax.imageio.ImageIO; import java.awt.*; import java.awt.image.BufferedImage; import java.io.File; import java.io.IOException; import java.text.DecimalFormat;     public class ImageDiff {       //不同的像素标记为红色     public static final int RGB_RED = 16711680;       //允许的Red，Green，Blue单个维度的像素差值     public static final int DIFF_ALLOW_RANGE = 5;       //不同像素点统计值     public static int diffPointCount = 0;       //从rgb值中抽取red     public static int getRed(int rgbValue){         return rgbValue & 0xff0000 >> 16;     }       //从rgb值中抽取green     public static int getGreen(int rgbValue){         return rgbValue & 0xff00 >> 8;     }       //从rgb值中抽取blue     public static int getBlue(int rgbValue){         return rgbValue & 0xff;     }       /**      * 比较两图片，并用红色标出不同的像素点，然后保存差异图片到本地，打印匹配率      * @param srcImgPath      * @param targetImgPath      */     public static void compareImages(String srcImgPath,String targetImgPath){         try {             BufferedImage srcImg = ImageIO.read(new File(srcImgPath));             BufferedImage targetImg = ImageIO.read(new File(targetImgPath));               diffPointCount = 0;             BufferedImage diffImg = srcImg;               int srcHeight = srcImg.getHeight();             int srcWidth = srcImg.getWidth();               //修改待比较图片的尺寸以适应源图片的尺寸             targetImg = changeImageSize(targetImg,srcHeight,srcWidth);               int srcRgb;             int targetRgb;               for(int h = 0;h<srcHeight;h++){                 for(int w=0;w<srcWidth;w++){                     srcRgb = srcImg.getRGB(w,h);                     targetRgb = targetImg.getRGB(w,h);                     if( Math.abs(getRed(srcRgb) - getRed(targetRgb))>DIFF_ALLOW_RANGE ||                             Math.abs(getGreen(srcRgb) - getGreen(targetRgb))>DIFF_ALLOW_RANGE||                             Math.abs(getBlue(srcRgb) - getBlue(targetRgb))>DIFF_ALLOW_RANGE){                         diffImg.setRGB(w,h, RGB_RED);                         diffPointCount++;                     }                 }             }               //保存差异图片             ImageIO.write(diffImg,"jpg",new File("diffImg.jpg"));             System.out.println("保存差异图片成功！");               //计算相似度(保留小数点后四位）             int totalPixel = srcHeight*srcWidth;             DecimalFormat decimalFormat = new DecimalFormat("#.####");             double matchRate = (totalPixel-diffPointCount)/(totalPixel*1.0);               System.out.println("图片相似度为： "+decimalFormat.format(matchRate)+"%");           }catch (Exception ex){             ex.printStackTrace();         }     }         /**      * 修改BufferedImage中的图片尺寸，以便和源图片进行比较      * @param image      * @param newHeight      * @param newWidth      * @return      */     public static BufferedImage changeImageSize(BufferedImage image,int newHeight,int newWidth){         Image img = image.getScaledInstance(newWidth,newHeight,Image.SCALE_SMOOTH);         int width = img.getWidth(null);         int height = img.getHeight(null);           //获取新图片的BufferedImage实例         BufferedImage newBufferedImage = new BufferedImage(width, height,                 BufferedImage.TYPE_INT_ARGB);         Graphics g = newBufferedImage.getGraphics();         g.drawImage(img, 0, 0, null);         g.dispose();         return newBufferedImage;     }       public static void main(String[] args){         compareImages("1.jpg","2.jpg");     } }