It's too difficult to change only one edge of the crop rectangle

[Theome]

Describe the bug If I try to crop an image so that only one side of the image is cut off, a zoom effect in the UI causes the opposite side of the image to also get cropped.

To Reproduce Suppose I want to crop the following image so that the purple part is cut off and the green square remains:

I open it in a TOCropViewController and I grab the top left corner of the white crop rectangle to position it at the point on the top edge of the image where the purple and green areas meet. It's practically impossible to move the finger exactly along the top edge, so as I don't want to cut off anything from the top of the image (the height of the image should stay the same), I move the finger through the black area above the top edge:

I finally reach the point with my finger, but during the movement the white corner stays exactly under my finger while the image zooms in. As a side effect, the right edge of the image moves off screen and if I let go, the resulting crop rectangle cuts off parts of the image on both the left and right side:

Expected behavior

I would expect that the white corner that I grabbed "snaps" so the image's top edge and slides along a horizontal line across the screen. The crop tool in the Photos app in iOS 14 behaves that way and it's much easier there to get the desired outcome.

iOS Device:

• Device: iPhone 11
• OS: iOS 14.3
• Library Version 2.6.0