Messages from Usenet group comp.lang.idl-pvwave, compiled by Paulo Penteado
What algorithm does the PLOTS routine use to compute pixel coords between (x1,y1) and (x2,y2) when the command PLOTS, [x1,x2],[y1,y2],/dev is executed. I would like to know the exact pixel coords between (x1,y1) and (x2,y2). After plotting the line, when I move the mouse, I get a new value for (x2,y2). So when I draw the new line, I want to erase the old line, and restore the underlying image. I can do this by PLOTS, XX(i),YY(i),color=image(xx(i),yy(i)),/dev where image is the underlying image, and xx, yy are arrays which contain the pixel coords between (x1,y1) and (x2,y2). Thanks for your help. Ratnakar Amaravadi Software/Hardware Engineer Department of Radiology I.U. School of Medicine (317)274-1843 (w) amaravad@indiana.edu (317)274-4074 (fax) ratty@foyt.indyrad.iupui.edu (317)632-5144 (res) http://www.indyrad.iupui.edu/~ratty/ratty.html
ratnakar amaravadi <amaravad@silver.ucs.indiana.edu> wrote: > > What algorithm does the PLOTS routine use to compute > pixel coords between (x1,y1) and (x2,y2) when the command > > PLOTS, [x1,x2],[y1,y2],/dev is executed. > > I would like to know the exact pixel coords between (x1,y1) and > (x2,y2). After plotting the line, when I move the mouse, I get a > new value for (x2,y2). So when I draw the new line, I want to > erase the old line, and restore the underlying image. I can do this .. If you are using an appropriate window manager, you might consider another approach: use the SET_GRAPHICS_FUNCTION keyword to the DEVICE command. Details are in the IDL Reference Guide, chapt.3. Then you can plot the line, then unplot it by changing the graphics function and repeating the same plots command.