How can I create a processor that uses the value of another field in a model?

[Hilton Campbell]

I'd like to create a processor for use in ImageSpecField that pulls a value from another field in the model. Specifically, I'd like the processor to crop the image, where the crop region is specified in a CharField ("left,top,right,bottom").

I tried but I have no idea how to do it. I then attempted to subclass ImageSpecField, with the idea that I could pass in the name of the crop field. I quickly got discouraged as I don't understand the internals of these classes.

Any idea how to go about this?

[matthewwithanm]

Hey Hilton! ImageSpec constructors get the source file (from which the model can be extracted), so you can accomplish this by writing a custom ImageSpec. There's a small example in the docstring of the get_field_info utility.

[Hilton Campbell]

Thanks for the great and fast response! I didn't realize there was more documentation than the Installation page... thanks to your suggestion, I found the Advanced Usage page and was able to accomplish what I wanted. Thanks for such a great library!

On Tue, Dec 10, 2013 at 11:21 AM, matthewwithanm <matthew...@gmail.com> wrote:

Hey Hilton! ImageSpec constructors get the source file (from which the model can be extracted), so you can accomplish this by writing a custom ImageSpec. There's a small example in the docstring of the get_field_info utility.

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[matthewwithanm]

Glad I could help. Thanks for the kind words!

[Nina Pavlich]

Hi Matthew, Hi Hilton,

I have follow-up question to Hilton's. (I just posted a topic here: https://groups.google.com/forum/#!topic/django-imagekit/eDD4kBkLPNc and then realized that I'm essentially tying to do exactly what Hilton described.)

The only thing I'm not sure about is if the value on the model changed -- for example if the thumbnail_width or thumbnail_height changed -- would this trigger an update on the ImageSpecField? Is there a recommended way to handle that situation? 

Thanks!

[matthewwithanm]

Hi Nina! Yeah, this will cause a new image to be generated. The processors are hashed to create the filename so any change you make to them will result in a new filename/file.

Hope that helps!