FireMonkey TBitmap StartLine Property C++ Code Sample

This example shows how to use the TBitmap.StartLine property. This example rotates the RGB channel color of every pixel of an image.

To build and test this example, create a FireMonkey HD Application - C++, then add the next objects to 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.

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);
	int I;
	Byte T;
	PAlphaColorRecArray PixelRecs;
	try {
		if (Image1->Bitmap->IsEmpty()) {
			// Display a message when there is no image loaded
			MessageDlg("There is no image to customize:",
				TMsgDlgType::mtWarning,
			TMsgDlgButtons() << TMsgDlgBtn::mbOK, 0);
		}
		else {
			// A copy of the initial bitmap
			MyBitmap->Assign(Image1->Bitmap);
			// Cast from 32-bit colors to color record
			PixelRecs = PAlphaColorRecArray(MyBitmap->StartLine);
			// Rotate RGB of every pixel
			for (I = 0; I < MyBitmap->Width * MyBitmap->Height - 1; I++) {
				T = (*PixelRecs)[I].R; // temp
				(*PixelRecs)[I].R = (*PixelRecs)[I].G;
				(*PixelRecs)[I].G = (*PixelRecs)[I].B;
				(*PixelRecs)[I].B = T;
			}
 
			// Display the result
			Image2->Bitmap = MyBitmap;
 
		}
	}
	__finally {
		delete MyBitmap;
	}
}