一段视频播放器文件代码，不明白

Question

代码如下：
import java.io.;
import java.util.TreeSet;
import java.awt.;
import java.awt.event.;
import java.awt.geom.AffineTransform;
import java.awt.image.;
import javax.imageio.;
import javax.swing.;

public class design1 extends Component {
DataInputStream data_in;
private byte[] yuv_array;
private int[] u_array, v_array;
private int[] rgb_array;
private BufferedImage img;
private int width, height;
private int frame_number;
private int frame_size, yuv_frame_size;

public design1(String filename, int width, int height, int frame_number) {
    this.width = width;
    this.height = height;
    frame_size = width * height;
    this.frame_number = frame_number;
    yuv_frame_size = (width * height * 3)>>1;
    //在Heap分配空间
    img = new BufferedImage(width, height, 1);//1:TYPE_INT_RGB
    yuv_array = new byte[yuv_frame_size];
    u_array = new int[frame_size];
    v_array = new int[frame_size];
    rgb_array = new int[frame_size];
    
    try {
        FileInputStream f_in = new FileInputStream(new File(filename));
        f_in.skip(frame_number * yuv_frame_size);
        data_in = new DataInputStream(f_in);
        data_in.read(yuv_array, 0, yuv_frame_size);
        this.frame_number++;
    } catch (IOException e) {  
        // TODO Auto-generated catch block  
        e.printStackTrace();  
    }
    yuv2rgb();
    img.setRGB(0, 0, width, height, rgb_array, 0, width);
}

private void yuv2rgb()
{
    int h;
    int h2;
    int frame_size2 = frame_size + (frame_size>>2);
    int width2 = width<<1;
    int i2, j2;
    
    h = 0;
    h2 = 0;
    for (int j = 0; j < (height>>1); j++)
    {
        for (int i = 0; i < (width>>1); i++)
        {
            i2 = i<<1;
            int a, b;
            u_array[h2 + i2]   = yuv_array[frame_size + h + i]&0xff;
            v_array[h2 + i2]   = yuv_array[frame_size2 + h + i]&0xff;
        }
        h += width>>1;
        h2 += width2;
    }
    //执行双线性内插，把4:1:1的YUV扩大为4:4:4的YUV
    h2 = 0;
    for (j2 = 0; j2 < height - 2; j2 += 2)
    {
        for (i2 = 0; i2 < width - 2; i2 += 2)
        {
            int a, b, ab;
            
            a = u_array[h2 + i2] + u_array[h2 + i2 + 2];//水平
            b = u_array[h2 + i2] + u_array[h2 + i2 + width2];//垂直
            ab = u_array[h2 + i2] + u_array[h2 + i2 + 2] + u_array[h2 + i2 + width2] + u_array[h2 + i2 + width2 + 2];//对角线
            u_array[h2 + i2 + 1] = (a + 1)>>1;
            u_array[h2 + i2 + width] = (b + 1)>>1;
            u_array[h2 + i2 + width + 1] = (ab + 2)>>2;
            
            a = v_array[h2 + i2] + v_array[h2 + i2 + 2];//水平
            b = v_array[h2 + i2] + v_array[h2 + i2 + width2];//垂直
            ab = v_array[h2 + i2] + v_array[h2 + i2 + 2] + v_array[h2 + i2 + width2] + v_array[h2 + i2 + width2 + 2];//对角线
            v_array[h2 + i2 + 1] = (a + 1)>>1;
            v_array[h2 + i2 + width] = (b + 1)>>1;
            v_array[h2 + i2 + width + 1] = (ab + 2)>>2;
        }
        u_array[h2 + i2 + 1] = u_array[h2 + i2];
        u_array[h2 + i2 + width] = 
        u_array[h2 + i2 + width + 1] = (u_array[h2 + i2] + u_array[h2 + i2 + width2] + 1)>>1;
        
        v_array[h2 + i2 + 1] = v_array[h2 + i2];
        v_array[h2 + i2 + width] = 
        v_array[h2 + i2 + width + 1] = (v_array[h2 + i2] + v_array[h2 + i2 + width2] + 1)>>1;
        
        h2 += width2;
    }
    for (i2 = 0; i2 < width - 2; i2 += 2)
    {
        int a, b, ab;
        
        u_array[h2 + i2 + 1] = 
        u_array[h2 + i2 + width + 1] = (u_array[h2 + i2] + u_array[h2 + i2 + 2] + 1)>>1;
        u_array[h2 + i2 + width] = u_array[h2 + i2];
        
        v_array[h2 + i2 + 1] = 
        v_array[h2 + i2 + width + 1] = (v_array[h2 + i2] + v_array[h2 + i2 + 2] + 1)>>1;
        v_array[h2 + i2 + width] = v_array[h2 + i2];
    }
    u_array[h2 + i2 + 1] =
    u_array[h2 + i2 + width] = 
    u_array[h2 + i2 + width + 1] = u_array[h2 + i2];       
    
    v_array[h2 + i2 + 1] =
    v_array[h2 + i2 + width] = 
    v_array[h2 + i2 + width + 1] = v_array[h2 + i2];
    
    //彩色空间变换,从YUV转换到RGB
    for (int i = 0; i < frame_size; i++)
    {
        int pixel_r, pixel_g, pixel_b;
        int pixel_y = yuv_array[i]&0xff;
        int pixel_u = u_array[i] - 128;
        int pixel_v = v_array[i] - 128;
        //YUV到RGB的矩阵变换运算
        double R = pixel_y - 0.001 * pixel_u + 1.402 * pixel_v;
        double G = pixel_y - 0.344 * pixel_u - 0.714 * pixel_v;
        double B = pixel_y + 1.772 * pixel_u + 0.001 * pixel_v;
        //限幅
        if (R > 255) pixel_r = 255;
        else if (R < 0) pixel_r = 0;
        else pixel_r = (int)R;
        if (G > 255) pixel_g = 255;
        else if (G < 0) pixel_g = 0;
        else pixel_g = (int)G;
        if (B > 255) pixel_b = 255;
        else if (B < 0) pixel_b = 0;
        else pixel_b = (int)B;
        rgb_array[i] = (pixel_r<<16) | (pixel_g<<8) | pixel_b;
    }
}

public Dimension getPreferredSize() {
    if (img == null) {
         return new Dimension(width, height);
    } else {
       return new Dimension(img.getWidth(null), img.getHeight(null));
   }
}

public void writeFile(String formatName, String filename) {
    try {
        ImageIO.write(img, formatName, new File(filename));
    } catch (IOException e) {
        e.printStackTrace();  
    }
}

public void paint(Graphics g) {
    g.drawImage(img, 0, 0, null);
}

public void play(JFrame f) {
    while(true){
        try {
            data_in.read(yuv_array, 0, yuv_frame_size);
            f.setTitle("YUV Player of GDUT              #" + frame_number + " frames");
            frame_number++;
        } catch (IOException e) {  
            // TODO Auto-generated catch block  
            e.printStackTrace();
        }
        yuv2rgb();
        img.setRGB(0, 0, width, height, rgb_array, 0, width);
        repaint(); 
    }
}

public static void main(String[] args) {
    // TODO Auto-generated method stub
    JFrame f = new JFrame("YUV Player of GDUT");
    f.addWindowListener(new WindowAdapter() {
        public void windowClosing(WindowEvent e) {System.exit(0);}
    });

    
    design1 me = new design1("ShuttleStart_1280x720.yuv", 1280, 720, 10);        
    f.add("Center", me);
    f.pack();
    f.setVisible(true);

    //me.writeFile("jpg", "out.jpg");
    //me.play(f);//连续读取并显示图像
}

}

Answer 1

就是把文件加载进来，将YUV数据转换成RGB颜色，然后用drawImage画出来