Thumbnails 对图片进行先缩放，再剪裁

最新推荐文章于 2023-02-15 14:44:17 发布

Alohazym

最新推荐文章于 2023-02-15 14:44:17 发布

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本文链接：https://blog.youkuaiyun.com/qq_41983336/article/details/117333173

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本文介绍了如何使用Thumbnailator库通过Canvas滤镜进行图片缩放并精确裁剪，以达到100x100的固定尺寸，同时保持原始比例。重点讲解了如何通过`newCanvas`方法配合大小和居中位置来实现定制缩略图需求。

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1. Thumbnails 对图片进行先缩放，再剪裁

Thumbnails 首先对图片进行缩放，缩放之后再进行剪裁出想要的大小

Thumbnails.of(inputStream).size(width,height).addFilter(new Canvas(width, height, Positions.CENTER)).outputQuality(0.8f).toOutputStream(response.getOutputStream());
主要是new Canvas(width, height, Positions.CENTER) 这个做剪裁

参考： https://github.com/coobird/thumbnailator/issues/22

关键原文：
If what is desired is to merely crop an image, Thumbnailator does not provide a 
direct way to do so, however there is a `Canvas` image filter which can perform 
image cropping. (Please refer the javadocs at 
http://thumbnailator.googlecode.com/hg/javadoc/net/coobird/thumbnailator/filters
/Canvas.html)

> 3. I will add empty area around to have exactly 100x100

The aforementioned `Canvas` image filter has a feature to forcefully make 
thumbnails a certain size.

For example, say we take a 200x400 image and scale it down to 50x100, then we 
want to have an empty area to make a 100x100 thumbnail. The code can be written 
as follows:

  Thumbnails.of("path/to/image-200x400")
    .size(100, 100)
    .addFilter(new Canvas(100, 100, Positions.CENTER))
    .toFile("path/to/thumbnail");

Note: `size(100, 100)` will preserve the aspect ratio of the original, so the 
thumbnail without the `Canvas` filter would be 50x100.

https://github.com/springcloud-zym/minio-util