灰度图像到矩阵，矩阵到灰度图像。

Question

我试图从灰度图像中获取2D矩阵并对其进行修改，然后返回到灰度图像。

但是，当试图将图像转换为矩阵时，像素返回黑色值。

我怎样才能找到解决这个问题的办法？

您可以在代码下面找到图像。

Java代码：

public class MyImageProcessing {
    private SampleModel sampleModel;
    public int[][] compute(File file)
{
try 
{
    BufferedImage img= ImageIO.read(file);
    Raster raster=img.getData();
    sampleModel = raster.getSampleModel();
    int w=raster.getWidth(),h=raster.getHeight();
    int pixels[][]=new int[w][h];
    for (int x=0;x<w;x++)
    {
        for(int y=0;y<h;y++)
        {
            pixels[x][y]=raster.getSample(x,y,0);
        }
    }

    return pixels;

}
catch (Exception e)
{
    e.printStackTrace();
}
return null;
}


    public void getImage(int pixels[][])
{
     int w=pixels.length;
     int h=pixels[0].length;
      WritableRaster raster= Raster.createWritableRaster(sampleModel, new Point(0,0));
     for(int i=0;i<w;i++)
     {
         for(int j=0;j<h;j++)
         {
             raster.setSample(i,j,0,pixels[i][j]);
         }
     }
BufferedImage image=new BufferedImage(w,h,BufferedImage.TYPE_BYTE_GRAY);
image.setData(raster);
File output=new File("C:\\Users\\salam\\Pictures\\3.png");
try {
    ImageIO.write(image,"png",output);
}
catch (Exception e)
{
    e.printStackTrace();
}
}

}

原始图像：

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从矩阵检索的图像：

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Answer 1

尝试这段代码.

如果这不是您所需要的，那么也许您可以从我的文章中删除的是，代码应该总是整洁、可读的、适当的缩进和注释，所有这些都增加了程序的可理解性。

注：您的图像在转换为灰度时返回几乎相同的黑白图像，因为您的图像是黑白的，非常类似于二值图像。

我还可以建议OpenCV (https://opencv.org/)，这是一个BSD许可，它简单，强大，并可用于Java -尽管我记得它是一个皮塔当安装在Ubuntu16.04。

import java.io.File;
import java.io.IOException;
import java.awt.image.BufferedImage;
import javax.imageio.ImageIO;

/**
 * This class converts images to grayscale color.
 */

public class GrayscaleConverter {

/**
 * Creates a new grayscaled BufferedImage object from the given source image
 * by averaging each pixels RGB value.
 * 
 * @param inputImageAbsPath the absolute path of the image file, including its name and extension.
 * @return a BufferedImage object.
 */
private BufferedImage compute(String inputImageAbsPath) {
    
    System.out.println("... Converting source image to gray scale.");
    
    BufferedImage img = null; // image file

    // Read the source image or throw an exception
    try {
        img = ImageIO.read(new File(inputImageAbsPath));
    } catch(Exception e) {
        e.printStackTrace();
    }

    // Get the image width and height dimensions
    int width = img.getWidth();
    int height = img.getHeight();

    // Convert to grayscale by looping over pixels, beginning at top-most left coordinate (0,0)
    for (int y = 0; y < height; y++) { // y = rows
        for (int x = 0; x < width; x++) { // x = columns
    
            // Get the pixel value at this (x,y) coordinate
            int p = img.getRGB(x,y);
    
            // Extract the alpha, R, G, B values from pixel p
            int a = (p>>24) & 0xff; // Shift bits and unsign
            int r = (p>>16) & 0xff;
            int g = (p>>8) & 0xff;
            int b = p & 0xff;
    
            // Calculate average color (grayscale it)
            int avg = (r+g+b)/3;
    
            // Replace RGB value with avg
            p = (a<<24) | (avg<<16) | (avg<<8) | avg;
            img.setRGB(x, y, p);
        }
    }
    return img;
}

/**
 * Saves the converted grayscale image. This method builds the save path from the provided file name,
 * file extension, and absolute path of the folder that you want to save the image in.
 * 
 * @param path the absolute path of the folder that you would like to save the image inside.
 * @param imageName the name you would like to save the image with.
 * @param imageFileType the image file extension, without the dot (.) preceding the image file type.
 * @param image the BufferedImage object returned from the compute method.
 */
private void saveImage(String path, String imageName, String imageFileType, BufferedImage image) {
    
    // Save or throw exception
    try {
        System.out.println("... Saving grayscale image to "
                + path.concat("\\").concat(imageName).concat(".").concat(imageFileType)); // save path displayed to user
        
        ImageIO.write(image,
                    imageFileType,
                    new File(path.concat("\\").concat(imageName).concat(".").concat(imageFileType)));
        
    } catch(Exception e) {
        e.printStackTrace();
    }
    System.out.println("... Image saved.");
}


// Driver
public static void main(String args[]) throws IOException {
    
    /*
     * Tested for .png and .jpg files. Both worked successfully.
     */
    
    // Test
    System.out.println("Testing GrayscaleConverter.\n");
    
    String input = "*source images absolute file path including name and extension*";
    String outputPath = "*absolute path to folder where you will save grayscale image in*";
    String outputFileName = "*save image with this name*";
    String outputFileType = "*save image with this file extension (no dot (.) e.g. png or jpg)*";
    
    GrayscaleConverter gsc = new GrayscaleConverter();
    BufferedImage convertedImage = gsc.compute(input);
    gsc.saveImage(outputPath, outputFileName, outputFileType, convertedImage );
    
    System.out.println("\nTest complete.");
}

}

提供的输入映像：

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输出图像：

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另一个示例输入图像：

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另一个示例输出映像：

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我用.png和.jpg图像文件测试了我的程序，它成功了。祝好运。