Java：如何检测格式并从图像中读取每个像素的 RGB 值？

Question

我一直在写一个批量图像处理的程序。图像有多种格式，但都是 JPEG、TIFF 或 PNG。我编写了以下用于存储和访问像素数据的类：

package imageReader;

import misc.NumberFunctions;

/**
 * A class to store pixel data and provide access to some of the pixel's     basic
 * attributes
 * 
 * @author Thomas
 *
 */
public class Pixel {

    /**
     * The X-coordinate of the pixel The left-most column of the image     is x=0
     */
    private int x;

    /**
     * The Y-coordinate of the pixel The top row of the image is y=0
     */
    private int y;

    /**
     * The red value of the pixel (from 0 to 255)
     */
    private int r;

    /**
     * The green value of the pixel (from 0 to 255)
     */
    private int g;

    /**
     * The blue value of the pixel (from 0 to 255)
     */
    private int b;

    /**
     * The highest color value in the pixel, which determine its brightness
     * (from 0 to 255)
     */
    private int value;

    /**
     * Creates an empty pixel object, setting it to black (0,0,0)
     * 
     * @param x
     *            the x-coordinate of the pixel
     * @param y
     *            the y-coordinate of the pixel
     */
    public Pixel(int x, int y) {
        this.x = x;
        this.y = y;
        this.r = 0;
        this.g = 0;
        this.b = 0;
        this.setValue();
    }

    /**
     * Get the x-coordinate of the pixel
     * 
     * @return the x-coordinate
     */
    public int getX() {
        return this.x;
    }

    /**
     * Get the y-coordinate of the pixel
     * 
     * @return the y-coordinate
     */
    public int getY() {
        return this.y;
    }

    /**
     * Get the red value of the pixel
     * 
     * @return the red value (0 - 255)
     */
    public int getRed() {
        return this.r;
    }

    /**
     * Get the green value of the pixel
     * 
     * @return the green value (0 - 255)
     */
    public int getGreen() {
        return this.g;
    }

    /**
     * Get the blue value of the pixel
     * 
     * @return the blue value (0 - 255)
     */
    public int getBlue() {
        return this.b;
    }

    /**
     * Get the brightness of the pixel
     * 
     * @return the value (0 - 255)
     */
    public int getValue() {
        return this.value;
    }

    /**
     * Get the brightness of the pixel
     * 
     * @return the value (0 - 100)
     */
    public double getValue100() {
        double value100 = ((double) this.value) / 2.55;
        return value100;
    }

    /**
     * Check if this Pixel object is set to the same location as another
     * 
     * @param otherPixel
     *            the other pixel
     * @return whether they share the same coordinates or not
     */
    public boolean hasSameLocation(Pixel otherPixel) {
        boolean xMatches = (this.getX() == otherPixel.getX());
        boolean yMatches = (this.getY() == otherPixel.getY());
        return (xMatches && yMatches);
    }

    /**
     * Checks if this pixel has the same color as another pixel
     * 
     * @param otherPixel
     *            the other pixel
     * @return whether they share the same color or not
     */
    public boolean hasSameColor(Pixel otherPixel) {
        if (this.getValue() != otherPixel.getValue())
            return false;
        boolean redMatches = (this.getRed() == otherPixel.getRed());
        boolean greenMatches = (this.getGreen() == otherPixel.getGreen());
        boolean blueMatches = (this.getBlue() == otherPixel.getBlue());
        if (redMatches && greenMatches && blueMatches)
            return true;
        else
            return false;
    }

    /**
     * An internal function for finding the brightness value of the pixel
     */
    private void setValue() {
        this.value = NumberFunctions.getMax(r, g, b);
    }
}

我想导入图像（我已经可以获取所有图像的路径），然后将每个图像的数据记录在 Pixel 对象的二维数组 (Pixel[][]) 中。为此，我需要你们的帮助来做三件事：

1. 确定图片类型并导入

2. 找出图像的尺寸

3. 读取每个像素的 RGB 值

感谢你们能给我的任何帮助。谢谢！

Answer 1

您可以使用此代码导入指定文件名的图像。这可能会引发 IOException，因此请注意这一点。

String path = "Image1.jpg";
File file = new File(path);
BufferedImage image = ImageIO.read(file);

图像类型对此并不重要，ImageIO 会自动检测它。如果你想在阅读后输入使用image.getType()

图片尺寸可取自BufferedImage

int width = image.getWidth();
int height = image.getHeight();

像素可以用image.getRGB(int x, int y) 读取，它返回一个整数颜色。你可以用构造函数Color c = new Color(int rgb)把它转换成java.awt.color然后用c.getRed()c.getGreen()c.getBlue(0)获取频道是一个简单的过程

如果我能给你一些建议，请不要复制数据。无需构建Pixels，只需编写您的方法以使用上述方法获取数据。正如其他人指出的那样，您的实现将占用更多内存。

Answer 2

使用BufferedImage：

try {
    BufferedImage image = ImageIO.read(new File("monkey.jpg")); // TODO actual file
    int width = image.getWidth();
    int height = image.getHeight();

    // TODO do whatever you want with image, for example get an rgb:
    Color color = new Color(image.getRgb(0,0));
} catch (IOException e) {
    // TODO handle
}

顺便说一句，这是丑陋的代码：

if (redMatches && greenMatches && blueMatches)
        return true;
    else
        return false;

替换为：

return redMatches && greenMatches && blueMatches;