UI Design for Touchscreens
February 4, 2013, Electronic Imaging Conference, Burlingame, CA—Thomas Bindre from Nik Software presented concepts for selective editing of images on touchscreen devices. The growth of smart mobile devices allows picture-taking capabilities anywhere, but the quality of most pictures is poor.
Editing can be a global operation, where all pixels are changed with some parameter, or selective, where variable filter parameters are invoked in distinct areas. For high-end work, tools like Photoshop allow fine grain control of all pixel parameters and various geometric selections functions. these tools are fine for graphics, but not as good for photos, because of the high complexity.
The use of control points is not the same as matte tools. They don’t allow for object detection and segmentation, but can support the superposition of many filters. For many details, the key is a distance function between pixels, and an associated adjustments of parameters. These can be easily accomplished with slider controls. Combining the control points and selective filtering, the user can use slide controls to adjust all parameters like brightness, contrast, saturation, and hue.
Tuning the tools for performance starts with a “lazy” filter that only changes the indicated areas of interest, and only at the existing resolution. First the tool has to break up the photo into tiles for processing, then add changes and smooth out the boundaries. One consideration is that the time to move to an object is a function of the distance and the width of the object (Fitt’s Law).
For desktop environments, the mouse cursor is mostly used in the center of the screen or for large widgets. For mobile devices, the finger is the control point, and is randomly located and always moving. As a result, they made the sliders across the full screen and use L-R movements to change the slider, and up-down movements to change the function. Pinch movements are for zoom functions. One example of this type of implementation is Snapseed, an iOS app that blends filter results.
