Creating Cropped Thumbnails With ImageMagick

/ PHP / by Paul Robinson / 8 Comments
This post was published back on February 24, 2009 and may be outdated. Please use caution when following older tutorials or using older code. After reading be sure to check for newer procedures or updates to code.

So you’ve just installed ImageMagick, but how do you make your thumbnails in it? Ahhh, a very good question my friend.

Why Not Use Imagick?

Well like my server, not all servers have the Imagick extention for PHP installed. Also I think (personal opinion, shock) the command line is a better way to use ImageMagick. Right let’s get to it.

How Do We Use ImageMagick From The Command Line?

Well in PHP we can use the exec() function. Some servers don’t allow you to use the command, but most, like mine, just disable the use of certain functions from that function.

Anyway here is the code I use to make square cropped thumbnails.

Unfortunately this will only work in versions of ImageMagick from 6.3.8-3 and upwards due to the use of -thumbnail along with the carat(^) symbol. Here is what to use if you have a lower version:

Of course for both of those commands you will need to change all the sizes to whatever you wish. Mine are 120px square as you can see. I also have my code only take in & output jpg files. For me this is fine, but if you want to have multiple formats you could just have pathinfo() run on the file name and use 120x120 '".$filename.".".$extention."' and it will convert any filetype to a jpg. Just remember that png or gif files with transparency will be saved with the transparent parts black.

That’s about it really. If you want any more info or if something I’ve wrote isn’t working let me know. 🙂


Author’s gravatar

Hey Paul, thank you for this piece of code. I was looking for something like this. However, I would also like it to take only the center portion of each image (landscape or portrait) and make a square thumbnail out of that. How can that be done?

Author’s gravatar author

The first code example in this tutorial should give you square thumbnails provided you have a version of IM either the same or higher than mentioned.

Author’s gravatar

Sorry, I was a bit vague. I want it to ‘zoom in’ on the center of the original image and then create a square thumbnail from that. Can that be done?

Author’s gravatar author

Ahh, sorry. I think it can but I’m away from my computer at the minute (sending this on my iPod) and I’m afraid I don’t know the code off the top of my head. I’ll drop you another comment when I’ve had a chance to have a look at my computer.

Author’s gravatar

What exactly does the carat do? Without it, there would be centered padding added because of the gravity. But does the carat actually crop to the desired size?

Author’s gravatar author

Hi Jan,

It’s been a while since I used ImageMagick since I don’t use it as often as I used to and if I do I generally use something like the excellent Intervention Library to interface with it, but hopefully I can answer your question.

By default IM will take your requested dimensions to be the maximum values and so will make sure neither the width or height of your scaled down image is larger than the requested size. So take, for example, our thumbnail command. It makes images 120×120. Let’s say we have a source image of 1280×720.

By default IM will take our image and shrink until the largest dimension of our source image fits inside the requested dimension. That should make our final image 120×67(.5) and you’d have a black background showing on the top & bottom because of gravity and since we set our extent geometry to 120×120.

If we add the ^ symbol IM will take our dimensions to be minimum sizes instead. So this time it can shrink the smallest dimension of our source image until it fits inside the requested dimension. That would make our source image shrink to 213(.3)x120 which is then centered because of gravity and then cropped because we set our extent to 120×120.

Sorry if that over explains. To answer your main questions though, no I don’t believe the caret does crop. It resizes the image in ratio but keeping it larger than the final dimensions so that no background is revealed. The extent settings actually cause the image to be cropped.

Edit: Corrected the sizes in the second example. Listed them in the wrong order.

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