CPSC 4050 / 6050

Spring 2014

Get the Picture!

Homework Project 1

Due: Tuesday, January 21, 2014

Problem Description:

You are to write a program that reads, displays, and writes out images from image files. The program should contain the following three distinct procedures: one to read from an image file into an RGBA pixmap, one to display the image stored in the RGBA pixmap in a window sized to exactly fit the image, and one to write an image file from an RGBA pixmap retrieved from the OpenGL display buffer. This will give you three key building blocks for future assignments, where you will be generating images and displaying them, saving the result, and reading image files to be used for texture maps.

You are to use ImageMagick's Magick++ library for the reading and writing of images, and to use OpenGL and GLUT for displaying images.

The program's user interface should respond to keyboard key presses as follows:

Basic Requirements:

The program should be named imgview, and should handle images stored in any format supported by ImageMagick. The file cube.ppm is a simple test image to try your program with. If your program works with this image, try it on the image file teapot.jpg, then try it on images of other sizes and formats.

The program should be named imgview and use an optional command line parameter to determine the initial input file name. For example, if the command line is

    imgview cube.ppm

the program will first read and display the image file named cube.ppm, before waiting for key presses to do any additional image reads or writes. If the program command line is simply

    imgview

then the program should display an empty window of a convenient size, with a black background.

As an assistance in displaying the image, you should be aware that the OpenGL routine glDrawPixels() will draw an entire array of pixel values to the display in one call. Likewise the OpenGL routine glReadPixels() will retrieve the current OpenGL display buffer and copy it into a pixmap. Check the course notes and the OpenGL documentation to get the details of how glDrawPixels() and glReadPixels are used. Note, that the RBGA format contains an alpha value as well as red, green, and blue values for each pixel. The alpha value is a measure of opacity, and is used for multiple image blending and compositing. For now you can simply set the alpha byte for each pixel to 255, which means fully opaque, or you can fetch the alpha value from the Magick++ image canvas, as we will discuss in class.

Advanced Extension:

Provide a reshape callback routine for your program, that responds to the user resizing the display window. If the user increases the size of the display window so that it is bigger than the image, the image should remain centered in the window (note that the OpenGL glViewport() command might come in handy for this). If the user decreases the size of the display window so that it is smaller than the image the image should be uniformly scaled down to the largest size that will still fit the window (note that the OpenGL command glPixelZoom() might come in handy for this).

General:

Please write the program in C++ , using OpenGL and GLUT graphics routines for the display. Make sure to put a comment header in each file of your code that gives a description of the program or object, your name, the date, and instructions on how it is used.