java代码如何实现图片的简单处理 java代码图像处理的入门技巧​

java.awt

javax.imageio

BufferedImage

BufferedImage

ImageIO

ImageIO

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

public class ImageProcessor {

    public static BufferedImage loadImage(String imagePath) {
        try {
            File file = new File(imagePath);
            if (!file.exists()) {
                System.err.println("图片文件不存在: " + imagePath);
                return null;
            }
            return ImageIO.read(file);
        } catch (IOException e) {
            System.err.println("加载图片失败: " + e.getMessage());
            return null;
        }
    }

    public static boolean saveImage(BufferedImage image, String outputPath, String format) {
        if (image == null) {
            System.err.println("要保存的图片为空。");
            return false;
        }
        try {
            File outputFile = new File(outputPath);
            // 确保输出目录存在
            if (!outputFile.getParentFile().exists()) {
                outputFile.getParentFile().mkdirs();
            }
            return ImageIO.write(image, format, outputFile);
        } catch (IOException e) {
            System.err.println("保存图片失败: " + e.getMessage());
            return false;
        }
    }

    public static void main(String[] args) {
        // 示例用法
        String inputPath = "path/to/your/image.jpg"; // 替换为你的图片路径
        String outputPath = "path/to/output/new_image.png"; // 替换为你的输出路径

        BufferedImage originalImage = loadImage(inputPath);
        if (originalImage != null) {
            System.out.println("图片加载成功，宽度: " + originalImage.getWidth() + ", 高度: " + originalImage.getHeight());
            // 假设这里对图片进行了某种处理，例如灰度化
            BufferedImage grayImage = convertToGrayscale(originalImage);
            if (saveImage(grayImage, outputPath, "png")) {
                System.out.println("图片成功保存到: " + outputPath);
            }
        }
    }

    // 灰度化方法将在下面详细说明
    public static BufferedImage convertToGrayscale(BufferedImage originalImage) {
        // ... (实现细节在下面)
        return originalImage; // 占位符
    }
}

    public static BufferedImage convertToGrayscale(BufferedImage originalImage) {
        if (originalImage == null) {
            return null;
        }
        int width = originalImage.getWidth();
        int height = originalImage.getHeight();
        // 创建一个新的BufferedImage，类型为TYPE_BYTE_GRAY，更适合灰度图
        BufferedImage grayImage = new BufferedImage(width, height, BufferedImage.TYPE_BYTE_GRAY);

        for (int y = 0; y < height; y++) {
            for (int x = 0; x < width; x++) {
                int rgb = originalImage.getRGB(x, y); // 获取像素的RGB值 (ARGB格式)
                int alpha = (rgb >> 24) & 0xFF; // 提取Alpha通道
                int red = (rgb >> 16) & 0xFF;   // 提取红色通道
                int green = (rgb >> 8) & 0xFF;  // 提取绿色通道
                int blue = rgb & 0xFF;          // 提取蓝色通道

                // 计算灰度值，常见算法有加权平均法
                // L = 0.299 * R + 0.587 * G + 0.114 * B
                int gray = (int) (0.299 * red + 0.587 * green + 0.114 * blue);

                // 将灰度值重新组合成RGB格式（R, G, B都设为gray），并保留原有的alpha通道
                int newRgb = (alpha << 24) | (gray << 16) | (gray << 8) | gray;
                grayImage.setRGB(x, y, newRgb);
            }
        }
        return grayImage;
    }

Graphics2D

    public static BufferedImage resizeImage(BufferedImage originalImage, int targetWidth, int targetHeight) {
        if (originalImage == null) {
            return null;
        }
        // 创建一个新的BufferedImage，指定目标尺寸和类型
        // 保持原图类型通常是个好选择，或者使用TYPE_INT_ARGB确保透明度支持
        BufferedImage resizedImage = new BufferedImage(targetWidth, targetHeight, originalImage.getType());
        java.awt.Graphics2D g2d = resizedImage.createGraphics();

        // 设置渲染质量，可选，但通常能提高缩放效果
        g2d.setRenderingHint(java.awt.RenderingHints.KEY_INTERPOLATION,
                             java.awt.RenderingHints.VALUE_INTERPOLATION_BILINEAR);
        g2d.setRenderingHint(java.awt.RenderingHints.KEY_RENDERING,
                             java.awt.RenderingHints.VALUE_RENDER_QUALITY);
        g2d.setRenderingHint(java.awt.RenderingHints.KEY_ANTIALIASING,
                             java.awt.RenderingHints.VALUE_ANTIALIAS_ON);

        // 绘制原图到新的BufferedImage上，自动进行缩放
        g2d.drawImage(originalImage, 0, 0, targetWidth, targetHeight, null);
        g2d.dispose(); // 释放Graphics2D资源
        return resizedImage;
    }

BufferedImage

    public static BufferedImage cropImage(BufferedImage originalImage, int x, int y, int width, int height) {
        if (originalImage == null) {
            return null;
        }
        // 检查裁剪区域是否有效
        if (x < 0 || y < 0 || x + width > originalImage.getWidth() || y + height > originalImage.getHeight()) {
            System.err.println("裁剪区域超出图片边界。");
            return null;
        }
        return originalImage.getSubimage(x, y, width, height);
    }

java.awt

javax.imageio

BufferedImage.getRGB(x, y)

int

int

(alpha << 24) | (red << 16) | (green << 8) | blue;

getRGB()

setRGB()

BufferedImage

Raster

Raster

getRGB

setRGB

Graphics2D

Graphics2D

AffineTransform

Graphics2D

Graphics2D

AffineTransform