Filling the abyss

In several cases an abyss (see Figure 127) is created between an image and the rectangle that encloses the image.

• When an image geometry is drawn using the TGrafPort::Draw function, you specify the image geometry and a rectangle. An abyss is created when the rectangle is larger than the image geometry.
• When you use the TImage::DrawPartial function, you specify the image graphic and a rectangle. An abyss is created when the rectangle is larger than the image graphic.
• When you change the position of the image (rotate it), or make it smaller (scale it), an abyss is created around the image because the coordinates of the original image are not changed by the transformation. The transformation is only in effect when the image draws.

The following code adds a blue abyss color to the image bundle. To keep the code concise, the code to create the image bundle and polygon is not shown.

TRGBColor blueColor( 0, 0, .5 );
2  TImageSamplingControl* imageSample = new TImageSamplingControl();
3  imageSample->SetAbyssColor( blueColor );
4  imageBundle->AdoptImageSampling( imageSample );
5  
6  TA8R8G8B8Image anRGBImage( TGPoint::kOrigin, 100, 100, imageBundle );
7  TGrafPort* imagePort->anRGBImage.GetGrafPort();
8  
9  imagePort->Draw( TGRect( 0,0, 200,200) );
10  aPolygon->Draw( *imagePort );
11  
12  anRGBImage.Draw( thePort );

Lines 2 through 3: Create a TImageSamplingControl with the default filtering method of kPointSampling. You get the default because no parameter is specified in the imageSample instantiation.

Line 3: Set the abyss color to blue in imageSample.

Lines 6 and 7: Create an image that is 100 world-coordinate units wide and high, and get the image port.

Lines 9: Draw a rectangle that is 200 world-coordinate units wide and high into the image port. Note that the image is smaller than the rectangle.

Line 10: Draw the polygon graphic into the image port.

Line 12: Draw the image. The area between the rectangle and the image fills with the blue abyss color.