Program: ED256 (Edge Detection). Download here (74K) - Note: you will need MFC42.DLL to run this.
There are a few more additions though. I experimented a little with various methods of edge detection with 256-colour pictures. I came up with three derivatives of LaPlace's algorithm - Difference-AND, Difference-OR, and Summation. Difference-AND will plot the point if all of the RGB-differences are above the threshold. Difference-OR will plot the point if any of the RGB-differences are above the threshold. Summation will plot the point if the sum of the RGB differences exceeds the threshold. You also have various output options. You can select to output in colour or monochrome. This has a surprising effect on some pictures - especially greyscale. Colour will output the colour of the difference - for example, if the program is currently looking at a white point surrounded by 8 red points, the program would plot (0,255,255) at the point. Monochrome will plot in black or white. There is a further option - the inverse option. The program starts off plotting white on black - that is, if a plot is not to be plotted then it plots white, and if in monochrome a plotted point will plot black. Sometimes it will be to your advantage, though, to swap that. The test picture of the F-22 is an excellent example of that. The threshold level is changed via the edit control on the toolbar. Invalid numbers are converted to 0 or 255 as appropriate. If a non-number is entered, for example "2p0" - then 2 is used as the threshold. This is a program I would like to see furthered a little. Unfortunately, I have neither the time nor the expertise required!! If there are any Win95 programmers out there who feel up to the task of improving the program, please do so! I would like to see better drawing (WM_PAINT messages invalidate the edges pictures), a save function, and improved algorithms and options. If anyone adds any of these features, please tell me about it, and I'll upload the new version (and give credit where due, of course). |
This program is a replacement to "Edge Detector", a simple dialog-based program that detected the edges of the Windows logo! As I had promised, this program will allow you to open any bitmap and run the edge detection algorithm on that.