Dezoomify FAQ

Ophir LOJKINE edited this page Dec 6, 2016 · 19 revisions

How to use dezoomify ?

Make sure you are using a recent web browser. Any recent version of Firefox or Chrome should work. Copy and paste the url of the webpage that contains your zoomable image to the text field on dezoomify, then press enter, and that should be all. Zoomify will automatically detect what kind of zoomable image it is, and how to download it. Once the image is fully loaded, right-click on it, and choose Save as. It may take some time, but your browser should eventually open a file dialog, asking you where you want to save the image, and save it (as a PNG file).

If it doesn't work, see the other questions below.

'Select automatically' doesn't work. How to know which radio box to check ?

The radio boxes allow you to choose the dezoomer used for your image. Sometimes, the name of the dezoomer will appear along with the image viewer. Sometimes, it doesn't. If so, you can try to right-click the zoomable image from your browser, then choose Inspect this element, and try to find clues about the dezoomer used in the code that appears. Alternatively,you can view the source code of the page using Ctrl-U on most browsers.

If you found the right dezoomer to use, but dezoomify still doesn't work, see the next point.

The page uses an image viewer supported by dezoomify, but dezoomify still doesn't work. What to do ?

Sometimes, dezoomify fails to find the required information file. You can try to find it yourself.

  • In the browser window that contains your zoomable image, open your browser's network inspector (Tools > Web development > Network in firefox). Open network console in firefox
  • Select XHR at the top of the inspector. network console XHR
  • Refresh the page (press F5). If not done already, display the zoomable image inside the page.
  • You will see all the resources loaded by the page appear in the network inspector. Search for the image information file. it's usually a small (< 5 Kb) .json, .xml, or .dzi file. For zoomify, this file is called ImageProperties.xml. Found meta file
  • Copy the URL of this small file. copy url
  • Paste the the URL to this information file to dezoomify. It should then be able to load your image.

The page uses an image viewer that is not supported by dezoomify. Is there still a chance ?

Yes, there is!

Dezoomify has a generic dezoomer, that tries to be clever and guess how many tiles there are, and stitch them together.

If your image is composed of multiple tiles, find the url of the tiles. For instance, you can use the Network inspector of your browser (Ctrl-Shift-Q on Firefox). Once you found an image url, try to spot inside it the coordinates of the tile inside the global image. Replace the horizontal coordinate by {{X}} and the vertical coordinate by {{Y}}.

Paste the resulting url in dezoomify. The generic dezoomer should be able to dezoom it.

Tutorial video

There is a tutorial video about the "generic dezoomer" on youtube: https://youtu.be/SY1dZe7MrUQ.

It still doesn't work

It might happen that the image format is a little unconventional, and that the generic dezoomer doesn't work.

In this case, a new dezoomer will have to be written. You may want to try and write your own dezoomer.

The image downloads, I can see it, but I cannot save it to my computer. How do I download it?

If your image is very large, it might happen that your web browser will display it, but crash or do nothing when you right-click and select "Save image as". Chrome in particular is known to be affected by this bug. There is nothing you can do about that, but use another browser. Firefox solved this bug not long ago, so you should be able to save even quite large images with it. In firefox, if the image is very large, the browser will freeze for a few seconds when you click "Save image as", but everything will work then.

See the very large images wiki page.

Dezoomify shows a progress bar, but my image appears to be completely blank.

This might be due to your browser limiting the maximum amount of memory it can allocate for any surface that will be drawn on screen (see this firefox bug for instance). This limitation is, at the time of writing, set to 500.000.000 on firefox. If the result of the height of your image x the width of your image x 4 is over this value, firefox will refuse to allocate memory for it, and display a white canvas.

On firefox, you can change this limit and thus display the image, but be warned, it's dangerous: if the limit is too low, your browser will refuse to render anything, and if it's too high, its big allocations may crash not only firefox, but also your graphic card driver.

To change this limit, in firefox, open a new page, and type about:config in the address bar. Click I accept the risk. Right-click anywhere in the list that appears, and choose New > Integer. Set the preference name to gfx.max-alloc-size, and the value to, for instance 2000000000. Resatart firefox. I would strongly advise that you do it only if you really need it, and set the value back to 500000000 once you've downloaded your image.

See the very large images wiki page.

I have too much money and want to give you some.

I don't accept donations, but if you want to pay for hosting the main dezoomify server, get in touch through github issues.

My problem isn't listed above.

First, try to desactivate all your browser plugins. Some poorly coded plugins may prevent dezoomify from working. If it still doesn't work, you may have discovered a bug in dezoomify. So you should open an issue here. Please include all the information that may help me solve your issue :

  • the URL of the web page containing your image
  • if you get a red error message, copy & paste it.
  • the name and version of your web browser
  • if your problem is hard to describe, you can include one or several screenshots.

And if you know javascript, your contributions are welcome :+1: