Description

This example shows how to use the TBitmap clear functions and their results.

The TBitmap's clear functions are Clear and ClearRect.

To build and test this example, create a FireMonkey HD Application - C++, and add the following objects on the form:

Two TImage objects
Two labels
A TGroupBox with two TRadioButton objects (a radio button for each function). Change the TRadioButton.Text property for each radio button with the name of a function.

Add a new bitmap as a global variable and name it MyBitmap. It will be used to save a copy of the initial bitmap.

Code

#pragma resource "*.fmx"
TForm1 *Form1;
TBitmap *MyBitmap;

Add the following code to the OnCreate event handler of the form. The code loads the bitmap into Image1, so it can be manipulated, and initializes MyBitmap.

void __fastcall TForm1::FormCreate(TObject *Sender)
{
 //Creates an empty bitmap
  MyBitmap = new TBitmap(0,0);
  //Loads the initial bitmap (to be manipulated) to Image1
  Image1->Bitmap->LoadFromFile("bitmap1.png");
}

Add the following lines of code to the OnChange event handlers of each radio button. The result will be displayed on the Image2.

Code

void __fastcall TForm1::RadioButton1Change(TObject *Sender)
{
        //A copy of the initial bitmap
  MyBitmap->Assign(Image1->Bitmap);
  //Clears the bitmap
  MyBitmap->Clear(claBlue);
  //Displays the result of the Clear function
  Image2->Bitmap =MyBitmap;
}
//---------------------------------------------------------------------------
 
void __fastcall TForm1::RadioButton2Change(TObject *Sender)
{
  //The rectangle to be cleared
 TRectF MyRect=TRectF(50,30,80,100);
 
  //A copy of the initial bitmap
  MyBitmap->Assign(Image1->Bitmap);
  //Clears the bitmap
  MyBitmap->ClearRect(MyRect);
  //Displays the result of the ClearRect function
  Image2->Bitmap=MyBitmap;
}