Question

我有一个广泛执行以下工作测试计划：

使用BufferedImage
将位移值转换为适当的数组
将值移位到整数
将值作为图像文件写回。

这很有效。

我正在尝试更改读取和写入图像文件之间的像素值。（在这种情况下，我试图更改红色组件中的第一个值。我使用测试打印机打印出值来查看更改。它显示它已更改，但是当再次读取新图像时（值已更改），该值是否保持不变？

下面是代码（它编译并运行） - 只需要取消注释该行以更改像素值，然后在读取新的更改图像时，再次注释掉该行以了解我的问题。

import java.awt.image.BufferedImage;
import java.io.*;
import javax.imageio.ImageIO;
import java.nio.*;
import java.util.*;

public class JPEGtester
{
   public static void main(String[] args)
   {
      int[] RGBarray = null;
      int w = 0;
      int h = 0;

      //Declare color arrays
      int [][] alphaPixels = null;
      int [][] redPixels = null;
      int [][] greenPixels = null;
      int [][] bluePixels =null;

      BufferedImage imgBuf =null;
      try
      { 
         //Read image file -- (WHEN VALUE IS CHANGED, CHANGE THE IMAGE NAME TO new-test.jpg)
         imgBuf = ImageIO.read(new File("test.jpg"));

         //Get width and hieght of image
         w = imgBuf.getWidth();
         h = imgBuf.getHeight();

         RGBarray = imgBuf.getRGB(0,0,w,h,null,0,w);

         alphaPixels = new int [h][w];
         redPixels = new int [h][w];
         greenPixels = new int [h][w];
         bluePixels = new int [h][w];

         //Bit shift values into arrays
         int i=0;
         for(int row=0; row<h; row++)
         {
            for(int col=0; col<w; col++)
            {
               alphaPixels[row][col] = ((RGBarray[i]>>24)&0xff);
               redPixels[row][col] = ((RGBarray[i]>>16)&0xff);
               greenPixels[row][col] = ((RGBarray[i]>>8)&0xff);
               bluePixels[row][col] = (RGBarray[i]&0xff);
               i++;
            }
         }

         //THIS IS TRYING TO CHANGE THE FIRST VALUE OF THE RED PIXEL IN THE ARRAY BY ADDING 1
         //UNCOMMENT THIS LINE TO CHANGE VALUES, AND THEN WILL PRINT OUT THE CHANGES VALUE IN THE TEST PRINTED ARRAY
         //THEN COMMENT THE LINE AND RE-RUN WITH THE NEW IMAGE. IT REMAINS UNCHANGED ?? (AS IF NEVER BEEN CHANGED)
         //redPixels[0][0] = redPixels[0][0]+1;

         //Test print the first 64 values of the Red Array
         for(int row=0; row<8; row++)
         {
            for(int col=0; col<8; col++)
            {
               System.out.print(redPixels[row][col]);
            }
         }

         //Set the values back to integers using re-bit shifting
         for(int row=0; row<h; row++)
         {
            for(int col=0; col<w; col++)
            {
               int rgb = (alphaPixels[row][col] & 0xff) << 24 | (redPixels[row][col] & 0xff) << 16 | (greenPixels[row][col] & 0xff) << 8 | (bluePixels[row][col] & 0xff);
               imgBuf.setRGB(col, row, rgb);
            }
         }

         //Write back image
         ImageIO.write(imgBuf, "jpg", new File("new-test.jpg"));
      }
      catch(IOException i)
      {};
   }
}

Answer 1

由于redPixels是一个单独的对象，从RGBArray复制的值是从缓冲的图像本身复制的，第一步是：

RGBArray[0] = redPixels[0][0] + 1;

imgBuf.setRGB(0,0,w,h,RGBArray,0,w);

由于有损压缩+ 1可能不足以影响不同的值。 + 10或更改相邻像素可能会有所帮助。

当然：

RGBArray[row * w + col] = ...[row][col];

或使用setRGB版本设置单个像素：

     for (int row = 0; row < h; row++)
     {
         for (int col = 0; col < w; col++)
         {
             int c = (alphaPixels[row][col] << 24)
                     | (redPixels[row][col] << 16)
                     | (greenPixels[row][col] << 8)
                     | (bluePixels[row][col]);
             imgBuf.setRGB(row, col, c);
         }
     }

在Java中更改像素值

1 个答案: