如何在现有图像文件的顶部添加20像素的白色？ [英] How to add 20 pixels of white at the top of an existing image file?

问题描述

我的图像尺寸为 w ，尺寸为 h 。在Java中，我需要创建尺寸为 w 乘以 h + 20 的图像，其中顶部 w x 20像素是白色，其余图像与原始图像相同。

I have an image of size w by h. In Java, I need to create an image that is size w by h+20 where the top w by 20 pixels is white, and the rest of the image is the same as the original image.

基本上，我想知道如何在现有缓冲图像的顶部添加20像素的白色。

Essentially I want to know how I can add 20 pixels of white to the top of an existing buffered image.

所以这有点像这样：

public static void main (String[] args) {
  BufferedImage originalImage = [the original image with a specific file path];
    ...code to create a new image 20 pixels higher...
    ...code to paint originalImage 20 pixels down on the new image
    ...code to save the new image...
}

推荐答案

建议：

1. 使用 GraphicsConfiguration.createCompatibleImage（int width，int height） 创建一个 BufferedImage 的宽度相同，但高度为+20。


2. 使用 BufferedImage.createGraphics（） 获取此图像的 Graphics2D 对象。


3. 使用 Graphics.setColor（Color c） 和 Graphics.fillRect（int x，int y ，int宽度，int高度） 绘制白色顶部


4. 使用 Graphics.drawImage（Image img，int x，int y，ImageObserver观察器） 将原始图像绘制到新图像的指定坐标。


5. 要保存新图像，请阅读编写/保存图像教程。

1. Use GraphicsConfiguration.createCompatibleImage(int width, int height) to create a BufferedImage of the same width, but with a height that's +20.
2. Use BufferedImage.createGraphics() to obtain the Graphics2D object of this image.
3. Use Graphics.setColor(Color c) and Graphics.fillRect(int x, int y, int width, int height) to draw the white top
4. Use Graphics.drawImage(Image img, int x, int y, ImageObserver observer) to draw the original image to the specified coordinates of the new image.
5. To save the new image, read the Writing/Saving an Image tutorial.

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import java.awt.Color;
import java.awt.FlowLayout;
import java.awt.Graphics2D;
import java.awt.GraphicsConfiguration;
import java.awt.GraphicsEnvironment;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;

import javax.imageio.ImageIO;
import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.SwingUtilities;

public class ImageManipulationDemo {
    private static BufferedImage ORIGINAL;
    private static BufferedImage ALTERED;
    private static final GraphicsConfiguration config = 
        GraphicsEnvironment.getLocalGraphicsEnvironment().getDefaultScreenDevice().getDefaultConfiguration();

    public static void main(String[] args) {
        try {
            loadImages();

            SwingUtilities.invokeLater(new Runnable(){
                @Override
                public void run() {
                    createAndShowGUI();             
                }
            });
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    private static void loadImages() throws IOException {
        ORIGINAL = ImageIO.read(
                ImageManipulationDemo.class.getResource("../resources/whitefro1.jpg"));
        ALTERED = config.createCompatibleImage(
                ORIGINAL.getWidth(), 
                ORIGINAL.getHeight() + 20);
        Graphics2D g2 = ALTERED.createGraphics();
        g2.setColor(Color.WHITE);
        g2.fillRect(0, 0, ALTERED.getWidth(), 20);
        g2.drawImage(ORIGINAL, 0, 20, null);
        g2.dispose();

        // Save image
        ImageIO.write(ALTERED, "PNG", new File("alteredImage.png"));
    }

    private static void createAndShowGUI() {
        final JFrame frame = new JFrame("Image Manipulation Demo");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.getContentPane().setBackground(Color.BLUE.darker());
        frame.getContentPane().setLayout(new FlowLayout());
        frame.getContentPane().add(new JLabel(new ImageIcon(ORIGINAL)));
        frame.getContentPane().add(new JLabel(new ImageIcon(ALTERED)));
        frame.pack();
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }
}

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