Seam examples. Black: horizontal seam. Gray: vertical seam. Green: not a seam -- contains more than one pixel from some columns.
One of the papers at SIGGRAPH that made news when it first came out was Seam Carving for Content-Aware Image Resizing by Shai Avidan and Ariel Shamir. In this assignment, you'll be implementing the basic algorithm presented therein. To wit, you'll be designing a program which can shrink an image (horizontally and/or vertically) to a given dimension. Your program should support the following usage
seamcarving input_image output_image output_width output_heightAn executable of my program is at:
~adamb/public/SeamCarving/seamcarving
For a brief overview of the algorithm and some inspiring results, check out the video. Your algorithm will shrink images as follows:
Feel free to use any energy function in the paper (or cook up something on your own). Defining a good energy function seems to be the key to achieving good results.
A horizontal seam is a connected path from one side of the image to the other that chooses exactly one pixel from each column. (A vertical seam is the same, but from top to bottom and with rows.) Finding the lowest-importance seam is a simple dynamic programming exercise. If you find yourself spending large amounts of time on it, please ask the course staff for help.
Your final code should be able to, given an input image, produce an output image shrunk to the specified number of pixels. A simple way to achieve this goal is to write your code to shrink only in one dimension and then create a wrapper function that transposes the image to shrink in the other dimension. I also highly recommend outputing your an image of your energy function mapped to greyscale values. I set each pixel to pow(energy(i,j)/max_energy, 1.0/3.0).
Notice how the content in the image is preserved, and the large, boring, area of asphalt is removed. (This does ruin the composition, but such is life.)
As you push the algorithm to its limits, artifacts -- such as shape distortions and odd cubist angles -- will begin to crop up. A lot of time on this project will be spent tweaking your code to mitigate these effects, as well as searching for pictures which don't exhibit them. Generally, highly-structured scenes and human faces will suffer, while scenes with textured objects on simple backgrounds will work better.
Implement the Scharr gradient operator.
Turn in this assignment electronically by pushing your source code to your proj6 GIT directory by 1:00 AM on the day of the deadline. We will be looking for multiple checkins documenting your development process.
As always, double check that you have submitted everything we need to build and run your submission, but no generated files (.o's, executables, or images). Be sure to include a Makefile that will build your project when we run 'make', and a readme.txt file telling us about your assignment. Do not forget to tell us what (if any) help did you receive from books, web sites or people other than the instructor and TA.