Java 如何使 BufferedImage 中的颜色透明并另存为 PNG
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How to make a color transparent in a BufferedImage and save as PNG
提问by corgrath
I have been searching the web for this, but I havent found any decent help.
我一直在网上搜索这个，但我没有找到任何像样的帮助。
I have a BufferedImage, which I have read in with ImageIO. Now I would like to make a certain color in that image to transparent, and save the image as PNG.
我有一个 BufferedImage，我用 ImageIO 读入了它。现在我想将该图像中的某种颜色设为透明，并将图像另存为 PNG。
I know I cannot just "paint" the transparent color for obvious reasons, so I am guessing I need some kind of a filter.
我知道出于显而易见的原因我不能仅仅“绘制”透明颜色，所以我猜我需要某种过滤器。
Anyone got some sample code for this?
有人有一些示例代码吗？
采纳答案by PhiLho
I did that recently, to answer a question of my project manager.
The function transforming gray to transparency is:
我最近这样做是为了回答我的项目经理的一个问题。
将灰色转换为透明的函数是：
private Image TransformGrayToTransparency(BufferedImage image)
{
ImageFilter filter = new RGBImageFilter()
{
public final int filterRGB(int x, int y, int rgb)
{
return (rgb << 8) & 0xFF000000;
}
};
ImageProducer ip = new FilteredImageSource(image.getSource(), filter);
return Toolkit.getDefaultToolkit().createImage(ip);
}
Actually, it acts on a gray-level image, so I just copy a RGB component (the R one) to alpha, discarding the others which are identical in my case.
You can adapt it to filter a specific color, eg. with a test of equality or range, etc.
Of course, the BufferedImage must be of BufferedImage.TYPE_INT_ARGB type.
实际上，它作用于灰度图像，所以我只是将 RGB 分量（R 分量）复制到 alpha，丢弃在我的情况下相同的其他分量。
您可以调整它以过滤特定颜色，例如。具有相等性或范围等的测试。
当然，BufferedImage 必须是 BufferedImage.TYPE_INT_ARGB 类型。
I don't address the question of saving, as it is pretty trivial, but I can add this code page too.
我不解决保存的问题，因为它非常简单，但我也可以添加此代码页。
[EDIT] To convert Image to BufferedImage:
[编辑] 将图像转换为 BufferedImage：
BufferedImage dest = new BufferedImage(
imageWidth, imageHeight,
BufferedImage.TYPE_INT_ARGB);
Graphics2D g2 = dest.createGraphics();
g2.drawImage(image, 0, 0, null);
g2.dispose();
[EDIT 2] I come after Christoffer posted his complete solution, but here is mine, I show how to make a range of colors transparent. Can be improved, eg. using HSB components instead.
[编辑 2] 我是在 Christoffer 发布他的完整解决方案之后来的，但这是我的，我展示了如何使一系列颜色透明。可以改进，例如。改用 HSB 组件。
import java.awt.*;
import java.awt.image.BufferedImage;
import java.awt.image.FilteredImageSource;
import java.awt.image.ImageFilter;
import java.awt.image.ImageProducer;
import java.awt.image.RGBImageFilter;
import java.io.*;
import javax.imageio.ImageIO;
public class AddTransparency
{
AddTransparency() throws IOException
{
String imagePath = "E:/Documents/images/";
File inFile = new File(imagePath, "map.png");
BufferedImage image = ImageIO.read(inFile);
Image transpImg1 = TransformGrayToTransparency(image);
BufferedImage resultImage1 = ImageToBufferedImage(transpImg1, image.getWidth(), image.getHeight());
File outFile1 = new File(imagePath, "map_with_transparency1.png");
ImageIO.write(resultImage1, "PNG", outFile1);
Image transpImg2 = TransformColorToTransparency(image, new Color(0, 50, 77), new Color(200, 200, 255));
BufferedImage resultImage2 = ImageToBufferedImage(transpImg2, image.getWidth(), image.getHeight());
File outFile2 = new File(imagePath, "map_with_transparency2.png");
ImageIO.write(resultImage2, "PNG", outFile2);
}
private Image TransformGrayToTransparency(BufferedImage image)
{
ImageFilter filter = new RGBImageFilter()
{
public final int filterRGB(int x, int y, int rgb)
{
return (rgb << 8) & 0xFF000000;
}
};
ImageProducer ip = new FilteredImageSource(image.getSource(), filter);
return Toolkit.getDefaultToolkit().createImage(ip);
}
private Image TransformColorToTransparency(BufferedImage image, Color c1, Color c2)
{
// Primitive test, just an example
final int r1 = c1.getRed();
final int g1 = c1.getGreen();
final int b1 = c1.getBlue();
final int r2 = c2.getRed();
final int g2 = c2.getGreen();
final int b2 = c2.getBlue();
ImageFilter filter = new RGBImageFilter()
{
public final int filterRGB(int x, int y, int rgb)
{
int r = (rgb & 0xFF0000) >> 16;
int g = (rgb & 0xFF00) >> 8;
int b = rgb & 0xFF;
if (r >= r1 && r <= r2 &&
g >= g1 && g <= g2 &&
b >= b1 && b <= b2)
{
// Set fully transparent but keep color
return rgb & 0xFFFFFF;
}
return rgb;
}
};
ImageProducer ip = new FilteredImageSource(image.getSource(), filter);
return Toolkit.getDefaultToolkit().createImage(ip);
}
private BufferedImage ImageToBufferedImage(Image image, int width, int height)
{
BufferedImage dest = new BufferedImage(
width, height, BufferedImage.TYPE_INT_ARGB);
Graphics2D g2 = dest.createGraphics();
g2.drawImage(image, 0, 0, null);
g2.dispose();
return dest;
}
public static void main(String[] args) throws IOException
{
AddTransparency at = new AddTransparency();
}
}
回答by corgrath
Thanks to PhilLo here is a complete solution of my demo application.
感谢 PhilLo，这里是我演示应用程序的完整解决方案。
public static void main(String[] args) throws Exception {
File in = new File("C:\Users\Christoffer\Desktop\christoffer.jpg");
BufferedImage source = ImageIO.read(in);
int color = source.getRGB(0, 0);
Image image = makeColorTransparent(source, new Color(color));
BufferedImage transparent = imageToBufferedImage(image);
File out = new File("C:\Users\Christoffer\Desktop\trans.PNG");
ImageIO.write(transparent, "PNG", out);
}
private static BufferedImage imageToBufferedImage(Image image) {
BufferedImage bufferedImage = new BufferedImage(image.getWidth(null), image.getHeight(null), BufferedImage.TYPE_INT_ARGB);
Graphics2D g2 = bufferedImage.createGraphics();
g2.drawImage(image, 0, 0, null);
g2.dispose();
return bufferedImage;
}
public static Image makeColorTransparent(BufferedImage im, final Color color) {
ImageFilter filter = new RGBImageFilter() {
// the color we are looking for... Alpha bits are set to opaque
public int markerRGB = color.getRGB() | 0xFF000000;
public final int filterRGB(int x, int y, int rgb) {
if ((rgb | 0xFF000000) == markerRGB) {
// Mark the alpha bits as zero - transparent
return 0x00FFFFFF & rgb;
} else {
// nothing to do
return rgb;
}
}
};
ImageProducer ip = new FilteredImageSource(im.getSource(), filter);
return Toolkit.getDefaultToolkit().createImage(ip);
}
