jdb@reef.cis.ufl.edu (Brian K. W. Hook) (01/12/91)
I am writing an app that uses an hexagonal map...each hex in the map has
its own bit map. I am running into the problem of how to use the Borland
Graphics interface (actually, ANY graphics library with a getimage/putimage
type function set) to write the hex bit map on the screen without writing
into the area of the rectangular bit map outside of the hex....e.g.
0011111100
0111111110
1111111111
0111111110
0011111100
I don't want ANYTHING written into the region with zeros. This wouldn't be
so hard if it was just black and white, but I am using 4-bit color. Does
anyone know of an easy method of overlay this rectangular block on the
screen but with only the hex part showing up?
thanks for the help,
Brianorpheus@reed.UUCP (P. Hawthorne) (01/13/91)
jdb@reef.cis.ufl.edu (Brian K. W. Hook) writes: | I am running into the problem of how to use the Borland Graphics interface | (actually, ANY graphics library with a getimage/putimage type function set) | to write the hex bit map on the screen without writing into the area of the | rectangular bit map outside of the hex....e.g. | | 0011111100 | 0111111110 | 1111111111 | 0111111110 | 0011111100 QuickDraw on the Macintosh has a procedure to allow you to copy one bitmap or pixmap to another, through a mask. It's a lot like a stencil, in that you can use a region to stop an image from being transfered outside that region. If I was going to try to do the same thing as the procedure I mentioned, without using it, I might try two methods first off. 1 Copy each pixel, from left to right and top to bottom, only if it is inside the area that you want to obliterate. Given that you are working with hexes, you might be able to develop an efficient algorithm to determine whether a given point is in or out of the hex. Alternately, if your graphics interface has the ability to define regions, you could define a hex at the appropriate scale when you began writing hexes, and use the mod operator and the interface call to see if the point was in the region. 2 Save the areas that you do not want to be obliterated, and replace them when you are done filling in the hex. If memory is an important consideration, you might be able to store the areas outside of the hex in a rectangle, by placing the upper left first, the lower right second, the lower left third, and the upper right fourth. Of course, that leave you in the position of having to solve the problem again.... I was implementing a Z Buffer the other day, which is a problem a lot like this one. The idea being that you step through each point on a surface, and only write the color of the surface onto pixels that are inside the area of the surface, and are closest to the eye. I had no problem determining if the point was closest to the eye. I had to use regions the determine if the point was inside the area of the surface. It was fortunate that the inside/outside test for regions in QuickDraw seems relatively quick. I'd be very interest to see any other solutions that are posted.
joe@proto.COM (Joe Huffman) (01/14/91)
In article <26275@uflorida.cis.ufl.EDU>, jdb@reef.cis.ufl.edu (Brian K. W. Hook) writes: > I am writing an app that uses an hexagonal map...each hex in the map has > its own bit map. I am running into the problem of how to use the Borland > Graphics interface (actually, ANY graphics library with a getimage/putimage > type function set) to write the hex bit map on the screen without writing > into the area of the rectangular bit map outside of the hex....e.g. [...example deleted...] This can be done with the graphics library that comes with the Zortech C/C++ compiler for the PC, under DOS, OS/2, and a couple DOS extenders. Use the fg_drawmatrix() function call. Further explaination available on request. disclaimer... I wrote the package. -- joe@proto.com
mcastle@mcs213f.cs.umr.edu (Mike Castle (Nexus)) (01/14/91)
In article <26275@uflorida.cis.ufl.EDU> jdb@reef.cis.ufl.edu (Brian K. W. Hook) writes: > > 0011111100 > 0111111110 > 1111111111 > 0111111110 > 0011111100 Clip you image to the hexagonal shape (such as by ANDing it with the above sample image). Using the same above sample image, do a PUTIMAGE with the NOTPut option. Now do a PUTIMAGE with the clipped image with the ORPut option. This may cause a slight flicker at the spot you are changing, but it should work. The hardest part will probably be clipping the image. If your pulling stuff off the screen to be moved, you might be able to clip it on a separate graphics page (not the current one). I haven't done much graphics programming yet, so I don't know how difficult that would be. If your creating a bunch a images for later use, then it will probably be no problem clipping it nicely. Hope this helps. BTW, anyone no how to access the 320x200x256 mode on a VGA? or is that SVGA only? I've seen lots of programs that use it, but can't seem to find any mention of it in either TPascal or TC++ manuals. I've picked up a couple of .BGI drivers, but I haven't had a chance to look at them. All my graphics programming will probably have to wait until summer. :-< Tanx. -- Mike Castle (Nexus) S087891@UMRVMA.UMR.EDU (preferred) | ERROR: Invalid mcastle@mcs213k.cs.umr.edu (unix mail-YEACH!)| command 'HELP' Life is like a clock: You can work constantly, and be right | try 'HELP' all the time, or not work at all, and be right twice a day. |
jpenne@ee.ualberta.ca (Jerry Penner) (01/14/91)
In article <26275@uflorida.cis.ufl.EDU> jdb@reef.cis.ufl.edu (Brian K. W. Hook) writes: > > 0011111100 > 0111111110 > 1111111111 > 0111111110 > 0011111100 [ How to draw hexagonal bitmaps? ] Well, What you do is make a bitmap that has 1 bits everywhere you want your hexagonal pattern to show through (ie. just like your example hexagon.) This I will call MASK. Your image I will call IMAGE. The data already on the screen I will call SCREEN. for each screen byte to modify get SCREEN xor IMAGE and MASK xor SCREEN now the screen data is put where mask == 0 and image data goes where mask == 1 put SCREEN Have fun. -- ------------- Jerry Penner alberta!bode!jpenne Edmonton, Alberta, Canada