FMXTBitmapCanvas (C++)

Description

This example shows how to use the TBitmap.Canvas property by drawing a rectangle on an image.

To build and test this example, create a Multi-Device Application - C++, then add the next objects on the form:

• A TImage to display the initial TBitmap.
• A TImage to display the result.
• Two TLabel, one for each TImage.
• A TButton to draw on the initial image.
• A TOpenDialog and a TButton to load the image to be customized.

Code

Add the following code to the OnClick event handlers of the load button.

void __fastcall TForm1::Button2Click(TObject *Sender) {
    if (OpenDialog1->Execute()) {
        Image1->Bitmap->LoadFromFile(OpenDialog1->FileName);
    }
}

Add the following code to the OnClick event handlers of the other button.

void __fastcall TForm1::Button1Click(TObject *Sender) {
    TBitmap *MyBitmap = new TBitmap(0, 0);
    // The rectangle to be drawn on the canvas
    TRectF MyRect = TRectF(50, 30, 150, 200);
    // A record on the stack, does not Free
    try {
        if (Image1->Bitmap->IsEmpty()) {
            // Display a message when there is no image loaded
            TDialogServiceAsync::MessageDialog(
                "There is no image to customize:",
                TMsgDlgType::mtWarning, TMsgDlgButtons() << TMsgDlgBtn::mbOK,
                TMsgDlgBtn::mbOK, 0);
        }
        else {
            // A copy of the initial bitmap
            MyBitmap->Assign(Image1->Bitmap);
            // Draw a rectangle on the copy
            MyBitmap->Canvas->BeginScene();
            MyBitmap->Canvas->Stroke->Kind = TBrushKind::Solid;
            MyBitmap->Canvas->Stroke->Color = claLime;
            MyBitmap->Canvas->StrokeThickness = 4;
            MyBitmap->Canvas->DrawRect(MyRect, 20, 20, AllCorners, 1.0);
            MyBitmap->Canvas->EndScene();
            // Display the result
            Image2->Bitmap = MyBitmap;
        }
    }
    __finally {
        delete MyBitmap;

    }
}

The result should look like in the following image:

Uses

• FMX.Graphics.TBitmap.Canvas ( fr | de | ja )

• FMX.Graphics.TCanvas.DrawRect( fr | de | ja )

• FMX.Objects.TImage.Bitmap( fr | de | ja )

See Also

• FMX.Objects.Objects.TImage ( fr | de | ja )
• FMX.Dialogs.TOpenDialog( fr | de | ja )
• Delphi version of this example