A UIImageView subclass that ignores touches on transparent pixels, based on OBShapedButton by Ole Begemann.

RMShapedImageView does it magic by overriding pointInside:withEvent:. This method is called to determine if a touch is inside the view. In our case, we only want to return YES if the corresponding pixels are not transparent (alpha > 0).

Usage

1. Add RMShapedImageView.h and RMShapedImageView.m to your project.
2. Replace your UIImageView with RMShapedImageView either in code or Interface Builder (by setting the Class of your UIImageView to RMShapedImageView).
3. Profit!

Configuration

Touches are inexact things and querying the alpha value of a single pixel might be too strict, even more so if the image is scaled down. Furthermore, if the image has shadows you might also want to ignore touches on them. RMShapedImageView has two configuration options to work around these problems:

• shapedTransparentMaxAlpha: maximum alpha value that will be considered transparent. 0 by default.
• shapedPixelTolerance: number of pixels around the point that will be examined. If at least one of them has alpha bigger than shapedTransparentMaxAlpha pointInside:withEvent: will return YES. 0 by default.

License

Copyright 2013 Robot Media SL

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.