Iphone frozen after setting contact photo?

A friend of mine sent me a photo of her so i could use it as a contact photo on my iphone 4, but when i did so, it took forever to set the photo so i tried pressing the top button to turn it off an now the phone is frozen with a weird, deformed version of the photo on the screen and i can't do anything with it. Is there a way to force shut down the phone so i can re start it?

Try to hard-reset it. Hold down both top button and home button for 8 seconds or so, until it shuts down.

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Delete all background running apps in the multitask bar so your iphone doesn't freeze that much. This became a habit of mine and my iphone hardly freezes/lags anymore.

Hard reset is somehow a method, but it may lose data in the process. Do you know there's free software to reboot frozen iPhone? Tenorshare ReiBoot. 100% free and safe, i tried it. Hope it helps.