I'm trying to create a trigger to resize a thumbnail on load to a default size of 110 x 83px. I can have the trigger reduce the width and height to those dimensions just fine, but the original picture size remains the same. I'd like to be able to cut down the actual size as you can do when creating an image variety trigger.
Can this be done through triggers? I notice a "size" attribute but I am unsure of what the proper value needs to be (or maybe I am misinterpreting what the size attribute does) as numbers have no apparent affect.
The Image Variety trigger will automatically create smaller images for you. You can then use the various variety keywords to display the variety (i.e. the resized image) instead of the original thumbnail.
I get the idea of creating a thumbnail by using the image variety trigger. But what if I want to upload 50 images at the same time, and some are horizontal, and some are vertical? If I set my thumbnail to a certain size, it will not be the correct aspect ratio for both horizontal and vertical, isn't this correct? Is there any way, to resize an image to a percent of the original? So that it would work for both horizontal and vertical images? So, I would be able set the trigger to make an image variety to 40% of the original image.
Also, when the trigger does add a thumbnail, why does it now show up on the details screen of that image?
Because thumbnails are usually designed to sit in a specific location and have either a fixed height or width (for layout purposes), the Create Image Variety trigger allows you to pick which dimension you want to constrain. The variety will then be created at the correct aspect ratio from the original but with the chose dimension maxed to the chosen value.
Also, the trigger is creating an Image Variety not setting a thumbnail. The image variety appears as a child of the image itself. You either have to setup another trigger to assign it as the thumbnail, or do that manually.
Which trigger would be used to achieve this?
[quote]Which trigger would be used to achieve this?
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You can do it using the Create Link trigger action. You want to create a NOTICE link with the link value of “thumbnail” – the image has to be the child in the Link, the parent is the asset that you want to assign the thumbnail to.
I am confused about this part. How do I link to the parent, if I have not uploaded the parent yet? I am just confused about what I am linking to, since I have not added the image yet.
[quote]I am confused about this part. How do I link to the parent, if I have not uploaded the parent yet? I am just confused about what I am linking to, since I have not added the image yet.
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This is why assigning thumbnails is confusing for triggers. 
When you upload the image, you can use triggers to create smaller versions as image varieties. You then need to manually assign those as thumbnails to other assets.
I guess it all depends on what you want to use thumbnails for.
Well probably the thumbnails would be used for a gallery. Also, when I try to manually set a thumbnail for a picture asset, it does not let me add the thumbnail, only the parent picture. Is something not right?
[quote]Well probably the thumbnails would be used for a gallery. Also, when I try to manually set a thumbnail for a picture asset, it does not let me add the thumbnail, only the parent picture. Is something not right?
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You don’t need to set thumbnails to use image varieties in a gallery. You can automatically list a particular variety instead of the parent asset when listing images.