是否可以导入PDF文件的栅格？

Question

Our office does scanning of data entry forms, and we lack any proprietary software that is able to do automated double-entry (primary entry is done by hand, of course). We are hoping to provide a tool for researchers to highlight regions on forms and use scanned versions to determine what participant entry was.

To do this, all I need for a very rough attempt is a file to read in PDFs as raster files, with coordinates as X, Y components, and B&W white "intensities" as a Z-axis.

We use R mainly for statistical analysis and data management, so options in R would be great.

Answer 1

You could use the raster package from R. However, it doesnt support .pdf files, but .tif,.jpg,.png (among many others). But coverting your pdfs into pngs shouldn't be a big problem: Look here for more information.

Once you have your png files ready, you can do the following:

png <- raster("your/png/file.png")

and then use the extract() function to get your brigthness value from the picture. Ie let's say your png is 200x200px and you want to extract a pixel value from row 100 and column 150:

value <- extract(png, c(150,100))