Draw an area over a Bitmap in C++ Builder?

i'm trying to write a program that one of its task is let the user to select an area over a bitmap.
The area must be select with a rectangle over this image. The user must press the mouse button,
to select the origin point, and then must move the mouse to the final point, and release the button,
to finish the selection. A rectangle must be painted while the user is moving the mouse from the origin
point to the final point, showing the area selected in each moment.

I've tried to do this with a canvas in a TImage object for the bitmap  but i can't clean every rectangle
that i paint while the mouse is moving to the final point.

      How can i write this program?
      what C++ Builder objects must i use?
ineilaAsked:
Who is Participating?
I wear a lot of hats...

"The solutions and answers provided on Experts Exchange have been extremely helpful to me over the last few years. I wear a lot of hats - Developer, Database Administrator, Help Desk, etc., so I know a lot of things but not a lot about one thing. Experts Exchange gives me answers from people who do know a lot about one thing, in a easy to use platform." -Todd S.

interCommented:
Dear ineila,

Do the following:(I am sure you do it partialy)

1 - Declare int OriginX, OriginY, OldX, OldY; BOOL drawing = false
2 - On MouseDown event of the TImage Set OriginX = x, OriginY = y
3 - On MouseMove event
    if (drawing) {
      Image1->Picture->Bitmap->Canvas->Rectangle(OrigingX,OriginY,OldX,OldY);
      OldX = x; OldY = y;
      Image1->Picture->Bitmap->Canvas->Rectangle(OrigingX,OriginY,OldX,OldY);
    } else {
      Image1->Picture->Bitmap->Canvas->Mode = pmXor; //this is the trick!!!!
      OriginX = x;OriginY = y;
      OldX = x; OldY = y;
      Image1->Picture->Bitmap->Canvas->Rectangle(OrigingX,OriginY,OldX,OldY);
      drawing = TRUE;
    }
4 - On MouseUp event
     if (drawing) {
      Image1->Picture->Bitmap->Canvas->Mode = pmCopy;
      drawing = FALSE;
     }

the idea is that when you want such a restoration, the pmXor mode help. The drawing you have made combines the colors with xor operation. If you draw the same thing second time the image became unaffected.

Need more, as more please
Igor


0

Experts Exchange Solution brought to you by

Your issues matter to us.

Facing a tech roadblock? Get the help and guidance you need from experienced professionals who care. Ask your question anytime, anywhere, with no hassle.

Start your 7-day free trial
interCommented:
Excuse me On MouseDown

  if (drawing) {
      Image1->Picture->Bitmap->Canvas->Mode = pmXor; //this is the trick!!!!
      OriginX = x;OriginY = y;
      OldX = x; OldY = y;
      Image1->Picture->Bitmap->Canvas->Rectangle(OrigingX,OriginY,OldX,OldY);
      drawing = TRUE;
  }

and DELETE the OnMouseMove ELSE part

Igor
0
interCommented:
Awfully sorry,

In previous comment If (drawing) be if (!drawing)..

igor
0
ineilaAuthor Commented:
The answer its good.

I have found another way, this is creating a TShape object over the Timage.
The algorithm is similar, when you press the mouse button i select the
origin position, and when i move the mouse i select the final position. When
mouse button is released the shape takes its final size.


0
It's more than this solution.Get answers and train to solve all your tech problems - anytime, anywhere.Try it for free Edge Out The Competitionfor your dream job with proven skills and certifications.Get started today Stand Outas the employee with proven skills.Start learning today for free Move Your Career Forwardwith certification training in the latest technologies.Start your trial today
C++

From novice to tech pro — start learning today.