如何阅读tif文件的子部分以便更快地导入？

问题描述

我需要循环读取数以千计的TIF文件（大小为3500x3500）。

I need to read thousands of TIF files (3500x3500 in size) in a loop.

而imread是最大的瓶颈。我只处理我有行col范围的图像的一小部分。

And imread is the biggest bottleneck. I only work on a small section of the image for which I have the row-col extent.

无论如何导入图像的子部分以改善导入过程大幅？还有其他任何建议吗？

Is there anyway to import a subsection of the image to improve the import process substantially? Any other suggestions?

这是代码的导入部分：

for m = 1:length(pFileNames)
    if ~exist(precipFileNames{m}, 'file')
        continue;
    end
    pConus = imread(pFileNames{m});
end

P.S。我尝试使用PixelRegions。但我有Matlab 2014，我收到此错误：

P.S. I tried to use PixelRegions. But I have Matlab 2014, and I get this error:

Undefined function or variable 'PixelRegion'.

推荐答案

考虑使用 vips at使用以下命令从每个图像中提取所需区域的命令行：

Consider using vips at the commandline to extract the area you want from each image with a command like:

vips extract_area INPUT.TIF OUTPUT.TIF left top width height

然后将其与 GNU Parallel 组合在一起做4或8一段时间，如下所示：

Then combine that with GNU Parallel to do 4 or 8 at a time, something like this:

parallel vips extract_area {} sub_{} left top width height ::: *.tif

我建议您在开始试验之前进行备份......

I suggest you make a backup before you start experimenting...

基准时间

我创建了1000张随机数据的TIF图像，全部大小为3,500x3500像素，然后运行 GNU Parallel + vips 命令从1,000个TIF中的每一个中提取100x100像素的区域。

I created 1,000 TIF images of random data, all sized at 3,500x3500 pixels and then ran the GNU Parallel + vips command above to extract an area of 100x100 pixels from each of the 1,000 TIFs.

在合理的规格iMac上，1,000个子提取图像并在11秒内写入磁盘。

On a reasonable spec iMac, the 1,000 sub images were extracted and written to disk in 11 seconds.

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