Tuesday, 16 August 2011

pdf and zip in google blogger

Google blogger allows only .png, .jpeg and .gif files to be uploaded as part of a blog post.

As my blog is somewhat technical, I want to be able to offer a zip file from time to time, containing sources I mention.

A first thought would be to rename the .zip to .png and tell the user to rename it after download, but even better is to have a chimera file which is both a .zip and a .png at the same time! The png could display the instruction to rename the file to .zip

I can then upload this .png file to google blogger which will display telling folk to download and rename to .zip

I've done this for a pdf in my blog post here where the thumbnail png brings up a large-png. If the large-png is saved to disk and renamed to .pdf, the pdf from which the thumbnail was taken is displayed.

This works because .png and .gif files have their magic at the beginning of the file, and .zip files and .pdf files have their magic at the end of the file. (The magic is the part of the file that is first read by the file viewer to work out how to treat the file).

Thus there is no deception. The chimera file is truly a .png file, and is truly a .zip file.

This example file here contains the instructions:
(right-click and save link/target as .zip not .png)
Be careful to save the link-target (the original and full sized image) and not the thumbnail.

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