BorlandTalk.com Borland discussion newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  How to overcome the problem of overlapping objects drawn wit          BorlandTalk.com Forum Index -> Delphi Graphics View previous topic :: View next topic   Author Message Tanju ÖZGÜR Guest Posted: Wed Jul 12, 2006 4:36 pm    Post subject: How to overcome the problem of overlapping objects drawn wit hi all, In my CAD application to select and deselect objects I use pmXor pen mode and user defined brush color to be used as rubberpen. For the overlapping objects rubberband is supposed to draw each object, but due to the pmXor pen-mode (probably) the second object is directly reflecting the background. Henceforth, as I can't change the Paint(), DrawObjecRubber, etc.. or other algorithms in my application, how can I avoid the overlapping objects reflecting the back-ground by making slight changes at the pen-mode or brush style? Best Regards, Back to top Roger Lascelles Guest Posted: Wed Jul 12, 2006 5:53 pm    Post subject: Re: How to overcome the problem of overlapping objects drawn "Tanju ÖZGÜR" <tanjuozgur (AT) yahoo (DOT) com> wrote in message news:44b4deb9$1 (AT) newsgroups (DOT) borland.com... Quote: hi all, Henceforth, as I can't change the Paint(), DrawObjecRubber, etc.. or other algorithms in my application, how can I avoid the overlapping objects reflecting the back-ground by making slight changes at the pen-mode or brush Not sure what is your question. But I can say this: Only the XOR mode lets you repeat a drawing operation to completely reverse it. There are no substitutes. However, you can pick your XOR draw color carefully. If you draw multiple times in XOR, you can remove it all by repeating all the drawing commands in XOR again. If you draw a line, or shape in XOR on top of a background, the effect of the background affects the color of the result. You can reduce this effect if your background does not vary greatly - for example, drawing over a series of pale, "washed out" (high white content) shapes can produce a vivid fairly uniform XOR. I use this trick. One solution is to go to the Graphics32 library which gives you the abstraction of layers in your drawing, so that erasing a layer does not erase the rest of the drawing on the other layers. With this, you can get any effect you want - I think you finally get forced toward Graphics32 or some other kind of offscreen bitmap management. Roger Lascelles Back to top Tanju ÖZGÜR Guest Posted: Wed Jul 12, 2006 6:29 pm    Post subject: Re: How to overcome the problem of overlapping objects drawn Hi Roger, Quote: Not sure what is your question. Sorry for my poor Eng. Quote: Only the XOR mode lets you repeat a drawing operation to completely reverse it. There are no substitutes. However, you can pick your XOR draw color carefully well, I think that's the main problem that I couldn't overcome. What if the objects are painted one on top of the other with the XOR pen-mode, if I draw the 2 overlapping objects in my drawing with rubberpen (XOR pen mode) the intersection area for these objects will be filled with background color, because XOR pen-mode completely reverse it. ( Please see the attachment) Quote: One solution is to go to the Graphics32 library which gives you the abstraction of layers in your drawing, so that erasing a layer does not erase the rest of the drawing on the other layers. With this, you can get any effect you want - I think you finally get forced toward Graphics32 or some other kind of offscreen bitmap management. Although I didin't check the latest developments of it, I had tried to use Graphics32 years ago when Alex Denisov has started to develop it. But I'm afraid that it does deal with raster images rather than vector drawings. And also for the CAD aplications performance is very slow. P.S. I couldn't succed to send the attachments I'll upload to the borland.public.attachments. Best Regards, "Roger Lascelles" <rogerlasAToptusnet.com.au>, haber iletisinde þunlarý yazdý:44b4f0c0 (AT) newsgroups (DOT) borland.com... Quote: "Tanju ÖZGÜR" <tanjuozgur (AT) yahoo (DOT) com> wrote in message news:44b4deb9$1 (AT) newsgroups (DOT) borland.com... hi all, Henceforth, as I can't change the Paint(), DrawObjecRubber, etc.. or other algorithms in my application, how can I avoid the overlapping objects reflecting the back-ground by making slight changes at the pen-mode or brush Not sure what is your question. But I can say this: Only the XOR mode lets you repeat a drawing operation to completely reverse it. There are no substitutes. However, you can pick your XOR draw color carefully. If you draw multiple times in XOR, you can remove it all by repeating all the drawing commands in XOR again. If you draw a line, or shape in XOR on top of a background, the effect of the background affects the color of the result. You can reduce this effect if your background does not vary greatly - for example, drawing over a series of pale, "washed out" (high white content) shapes can produce a vivid fairly uniform XOR. I use this trick. One solution is to go to the Graphics32 library which gives you the abstraction of layers in your drawing, so that erasing a layer does not erase the rest of the drawing on the other layers. With this, you can get any effect you want - I think you finally get forced toward Graphics32 or some other kind of offscreen bitmap management. Roger Lascelles Back to top Tanju ÖZGÜR Guest Posted: Wed Jul 12, 2006 6:34 pm    Post subject: Re: How to overcome the problem of overlapping objects drawn Roger please see the "borland.public.attachments" newsgroup to see the image the subject is same as this. "Tanju ÖZGÜR" <tanjuozgur (AT) yahoo (DOT) com>, haber iletisinde þunlarý yazdý:44b4f91d$1 (AT) newsgroups (DOT) borland.com... Quote: Hi Roger, Not sure what is your question. Sorry for my poor Eng. :) Only the XOR mode lets you repeat a drawing operation to completely reverse it. There are no substitutes. However, you can pick your XOR draw color carefully well, I think that's the main problem that I couldn't overcome. What if the objects are painted one on top of the other with the XOR pen-mode, if I draw the 2 overlapping objects in my drawing with rubberpen (XOR pen mode) the intersection area for these objects will be filled with background color, because XOR pen-mode completely reverse it. ( Please see the attachment) One solution is to go to the Graphics32 library which gives you the abstraction of layers in your drawing, so that erasing a layer does not erase the rest of the drawing on the other layers. With this, you can get any effect you want - I think you finally get forced toward Graphics32 or some other kind of offscreen bitmap management. Although I didin't check the latest developments of it, I had tried to use Graphics32 years ago when Alex Denisov has started to develop it. But I'm afraid that it does deal with raster images rather than vector drawings. And also for the CAD aplications performance is very slow. P.S. I couldn't succed to send the attachments I'll upload to the borland.public.attachments. Best Regards, "Roger Lascelles" <rogerlasAToptusnet.com.au>, haber iletisinde þunlarý yazdý:44b4f0c0 (AT) newsgroups (DOT) borland.com... "Tanju ÖZGÜR" <tanjuozgur (AT) yahoo (DOT) com> wrote in message news:44b4deb9$1 (AT) newsgroups (DOT) borland.com... hi all, Henceforth, as I can't change the Paint(), DrawObjecRubber, etc.. or other algorithms in my application, how can I avoid the overlapping objects reflecting the back-ground by making slight changes at the pen-mode or brush Not sure what is your question. But I can say this: Only the XOR mode lets you repeat a drawing operation to completely reverse it. There are no substitutes. However, you can pick your XOR draw color carefully. If you draw multiple times in XOR, you can remove it all by repeating all the drawing commands in XOR again. If you draw a line, or shape in XOR on top of a background, the effect of the background affects the color of the result. You can reduce this effect if your background does not vary greatly - for example, drawing over a series of pale, "washed out" (high white content) shapes can produce a vivid fairly uniform XOR. I use this trick. One solution is to go to the Graphics32 library which gives you the abstraction of layers in your drawing, so that erasing a layer does not erase the rest of the drawing on the other layers. With this, you can get any effect you want - I think you finally get forced toward Graphics32 or some other kind of offscreen bitmap management. Roger Lascelles Back to top somebody Guest Posted: Wed Jul 12, 2006 10:18 pm    Post subject: Re: How to overcome the problem of overlapping objects drawn "Tanju ÖZGÜR" <tanjuozgur (AT) yahoo (DOT) com> wrote Quote: In my CAD application to select and deselect objects I use pmXor pen mode Easy answer to all question of the same sort: Don't ever use XOR drawing. It's a remnant from the bad old days of slow graphics hardware and limited color depth (indexed colors). If you need performance, use some sort of spatial partitioning and back buffers. Headaches will instantly go away and your application will be scalable instead of constantly hitting brick walls when you need to update functionality. Back to top Tanju ÖZGÜR Guest Posted: Wed Jul 12, 2006 10:37 pm    Post subject: Re: How to overcome the problem of overlapping objects drawn Actually I'm using the double-buffer to avoid flickering (performance is quite satisfactory) and as I said on my previous posts it's not easy to change all the framework of application because I've done a lot of work so far. Isn't there other ways ( with pen-modes ). "somebody" <A>, iletide þunu yazdý news:44b52ebd (AT) newsgroups (DOT) borland.com... Quote: "Tanju ÖZGÜR" <tanjuozgur (AT) yahoo (DOT) com> wrote In my CAD application to select and deselect objects I use pmXor pen mode Easy answer to all question of the same sort: Don't ever use XOR drawing. It's a remnant from the bad old days of slow graphics hardware and limited color depth (indexed colors). If you need performance, use some sort of spatial partitioning and back buffers. Headaches will instantly go away and your application will be scalable instead of constantly hitting brick walls when you need to update functionality. Back to top Roger Lascelles Guest Posted: Thu Jul 13, 2006 4:15 am    Post subject: Re: How to overcome the problem of overlapping objects drawn "Tanju ÖZGÜR" <tanjuozgur (AT) yahoo (DOT) com> wrote in message news:44b4fa82$1 (AT) newsgroups (DOT) borland.com... Quote: Roger please see the "borland.public.attachments" newsgroup to see the image > the subject is same as this. Nice clear drawing! I am sorry, but the image cannot be made better with XOR. CAD programs don't use XOR, instead they keep track of what needs to be redrawn. For example, you can draw a line in selected color, then redraw it in unselected color when you want to turn off the selection. If your code is organised so you can paint each object separately, then you can paint any object in any color. CAD programs keep track of what needs to be redrawn, often as rectangular areas. All objects which overlap the redraw area are redrawn. I have used a compromise possible between XOR and COPY pens : draw the whole image in COPY pen, and use XOR for objects which are being dragged. Users can accept the unusual colors for dragging. When the drag is finished, redraw the source rectangle and all objects overlapping it, so that the moved item "disappears". Then redraw the moved object in its normal colors. People have posted to this newsgroup who mention using Graphics32 for line drawing, so I think you need to look at it again. Apparently you can use standard GDI drawing functions or special drawing functions with Graphics32, so you can use your existing painting code. You have done a lot of work to bring your CAD program this far! But there is more work to come! 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