在 Java 中按多边形区域裁剪图像 [英] Crop image by polygon area in Java

问题描述

通过使用 Canvas 和 JS，我可以绘制这样的形状并获得每个点的 x,y:

Tha 区域可以通过 4 个以上的点来选择，看看这个

我用过...

BufferedImage source = ImageIO.read(new File("Example.jpg"));GeneralPath 剪辑 = new GeneralPath();剪辑.moveTo(65, 123);clip.lineTo(241, 178);clip.lineTo(268, 405);clip.lineTo(145, 512);剪辑.closePath();矩形边界 = clip.getBounds();BufferedImage img = new BufferedImage(bounds.width, bounds.height, BufferedImage.TYPE_INT_ARGB);Graphics2D g2d = img.createGraphics();clip.transform(AffineTransform.getTranslateInstance(-65, -123));g2d.setClip(剪辑)；g2d.translate(-65, -123);g2d.drawImage(source, 0, 0, null);g2d.dispose();ImageIO.write(img, "png", new File("Clipped.png"));

生成...

现在，图像是矩形的，这就是它的工作方式

现在，setClip 相当粗糙，不受任何RenderingHints 的影响，您可以改用软剪辑"，这更复杂，但会生成更好的结果.请参阅此示例和这个例子了解更多详情

by using Canvas and JS I can draw a shape like this and have the x,y of each point :

Tha area can be choosen by more than 4 points, look at this link to have an idea.

I need to save and crop the image of the selected area by using the points. I can not use BufferedImage as it is just rectangular. Which lib in java I can use?

解决方案

Okay, so starting with...

I used...

BufferedImage source = ImageIO.read(new File("Example.jpg"));
GeneralPath clip = new GeneralPath();
clip.moveTo(65, 123);
clip.lineTo(241, 178);
clip.lineTo(268, 405);
clip.lineTo(145, 512);
clip.closePath();

Rectangle bounds = clip.getBounds();
BufferedImage img = new BufferedImage(bounds.width, bounds.height, BufferedImage.TYPE_INT_ARGB);
Graphics2D g2d = img.createGraphics();
clip.transform(AffineTransform.getTranslateInstance(-65, -123));
g2d.setClip(clip);
g2d.translate(-65, -123);
g2d.drawImage(source, 0, 0, null);
g2d.dispose();

ImageIO.write(img, "png", new File("Clipped.png"));

to generate...

Now, the image is rectangular, that's just the way it works

Now, setClip is quite rough and isn't effect by any RenderingHints, you could make use of "soft clipping" instead, which is more involved, but generates a nicer results. See this example and this exmaple for more details

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