# thumbcache
利用Windows的thumbcache获取文件的BMP格式预览图。
## 使用方法
尝试获取非图片文件（如.zip或.exe）的预览会导致错误。
```rs
use std::io::{Error, Write};
pub fn main() -> Result<(), Error> {
let bmp = thumbcache::get_bmp(r"C:\文件路径.jpeg", thumbcache::ThumbSize::S96)?;
let mut file_out = std::fs::File::create("./out.bmp")?;
let _ = file_out.write_all(&bmp);
Ok(())
}
```
## 示例
### 将BMP转换为JPEG
Windows只能返回BMP格式，但有时这个格式可能不太方便。这个示例使用[image](https://github.com/image-rs/image) crate将BMP转换为JPEG。
```rs
use thumbcache::{get_bmp};
use image::{load_from_memory};
fn main() {
let bmp = get_bmp(r"C:\文件路径.jpeg", thumbcache::ThumbSize::S256).unwrap();
let image = load_from_memory(&bmp).unwrap();
let mut buf: Vec<u8> = Vec::new();
let mut writer = std::io::Cursor::new(&mut buf);
image.write_to(&mut writer, image::ImageFormat::Jpeg).unwrap();
std::fs::write("./output.jpeg", buf).unwrap();
}
```
## 参考来源
https://stackoverflow.com/questions/14207618/get-bytes-from-hbitmap
https://stackoverflow.com/questions/21751747/extract-thumbnail-for-any-file-in-windows
https://learn.microsoft.com/en-us/windows/win32/api/shobjidl_core/nf-shobjidl_core-ishellitemimagefactory-getimage