Understanding IIIF Image Presentation
Working with IIIF Images
(In-class exercise)
Using IIIF can be a very complex business, but the idea behind it is that it should be accessible for relatively simple uses as well. Behind the scenes, the library IT staff has made your access to IIIF images fairly straightforward by hosting them in their own IIIF server (we're Carleton's first IIIF pilot project!). The previous page has laid out some of the key url's to access the images, but here we will try to take you through a more practical introduction to them.
Navigate in your browser to the address below to see all the images we have of the images for the manuscripts and manuscript fragments in Carleton's collection.
The library viewer that you see referenced in the url above allows you to download directly all the image files that we have hosted on the IIIF server, but is NOT the server itself. It may be necessary, however, to use the files names listed there to figure out what the complete address for the IIIF server of your images are.
Using the above webpage, track down the file name for the (at minimum) two images associated with the folio you worked on last term. For example, if you were working on the CUAG folio no. 13, you would find these two files listed:
In order to see the above image from the IIIF server, the above image file name (2) needs to be sandwiched between the prefix (1) identifying the location of the IIIF server and the suffix (3) which specifies how the server should present the image you have requested.
Put together, your browser will show you the image you have requested. Try this with your folio. It might take a couple attempts to make sure you have all the parts of the address right. When using this set up (i.e. with this suffix), the whole image is served up and allows you to switch between a full zoom and the zoom to fit your screen.
The suffixes, however, allow you to select only parts of the image and the degree of zoom you may request. The suffix, however, allows you to play with this. I suggest you take a look at:
an IIIF Image API Playground set up by Stanford, which allows you to play with the settings of the images served to you
Basically the parameters allow you to specify what size, what part of the images, what colour and at what magnification of the image the server sends out.
In the example above, the suffix part of the address for CUAG fol. 13 reads:
The first /full means that the entire region of the image is displayed. The second /full means the largest size will be displayed. The /0 means that the original rotation is maintained and the/default.jpg means that the default quality (i.e. colour type) is offered.
Region
You can change the region to be only a portion of the photo, presenting only a square for example, or a defined region of the image. We'll do both with the image we have been looking at:
The server can automatically serve up the image as a square [Click on the link]
In the second image, you should see only a small selection of the image [Psalmus: Domini], as below:
The suffix for this image is:
/1200,2050,1040,250/full/0/default.jpg
Instead of /full, we now have a series of numbers separated by commas. These are coordinates. The first /1200 indicates that the selection of the image begins at pixel 1200 on the horizontal axis. The second number 2500 specifies that the selection of the image begins at pixel 2050 on the vertical axis. 1040 indicates that the selection is 1040 pixels in width, and 250 indicates that it is 250 high (progressing rightwards and downwards from the specified starting points).
If you are using Chrome as your browser you can easily install a "page ruler" extension, such as this one, to visualize the pixel locations of images.
Size
Without changing the pixels locations specified above, we might only want to see this image at half the original size (or 50 percent).
Looks like this (it should be smaller than the other one unless your browser window is narrow and has auto-adjusted the size of the images):
You can also specify two values separated by a comma in order to define width and height instead of percentage size.
Rotation
You can rotate, by supplying the third value with a number between 0 and 360 degrees. The following is rotated 180 degrees:
Quality
Ideally, you can substitute "bitonal" or "gray" of "color" (note American spellings) for default.jpg, but this doesn't seem to be working in our case. So, well, trust me that it can work.
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