2D and 3D GRAPHICS

Example

To shows how easy it is to instantiate and use a transfer mode classes, an example is shown before describing the transfer mode classes. This example draws two polygons into an image. Each polygon has a white fill and a blue frame, but the opacity values are different. Figure 115 shows how this code looks at runtime.

  Copyright ©  Taligent, Inc. 1995
1  TColorPaint* whiteFrame = new TColorPaint( TRGBColor( GIntensity(1), GIntensity(1),
2                                              GIntensity( 1) ) );
3  TColorPaint* blueFill = new TColorPaint( TRGBColor( GIntensity(0), GIntensity(0),
4                                              GIntensity(1), GIntensity(1) ) );
5  TGrafBundle* polyBundle = new TGrafBundle( blueFill, whiteFrame,
6                                              TAttributeState::kFillAndFrame );
7  TSolidPen* centerFramePen = new TSolidPen( 5.0 );
8  polyBundle->AdoptFramePen( centerFramePen );
9  
10  TColorPaint* whiteFrame2 = new TColorPaint( TRGBColor( GIntensity(1), GIntensity(1),
11                                              GIntensity( 1), GIntensity(.5) ) );
12  TColorPaint* blueFill2 = new TColorPaint( TRGBColor( GIntensity(0), GIntensity(0),
13                                              GIntensity(1), GIntensity( .5 ) ) );
14  TGrafBundle* polyBundle2 = new TGrafBundle(  blueFill2, whiteFrame2,
15                                              TAttributeState::kFillAndFrame );
16  TSolidPen* centerFramePen2 = new TSolidPen( 5.0 );
17  polyBundle2->AdoptFramePen( centerFramePen2 );
18  
19  TColorPaint* redFillColor = new TColorPaint( TRGBColor( GIntensity(.75), GIntensity(.25), GIntensity(.25), GIntensity( 1 ) ) );
20  TGrafBundle redBundle( redFillColor, TAttributeState::kFill );
21  
22  TGrayInvertSrcTransferMode* frameTransferMode = new TGrayInvertSrcTransferMode();
23  TGrayInvertSrcTransferMode* fillTransferMode = new TGrayInvertSrcTransferMode();
24  polyBundle->AdoptFrameTransferMode( frameTransferMode );
25  polyBundle->AdoptFillTransferMode( fillTransferMode );
26  
27  TSrcCopyTransferMode* frameTransferMode2 = new TSrcCopyTransferMode();
28  TSrcCopyTransferMode* fillTransferMode2 = new TSrcCopyTransferMode();
29  polyBundle2->AdoptFrameTransferMode( frameTransferMode2 );
30  polyBundle2->AdoptFillTransferMode( fillTransferMode2 );
31  TGPolygon aPolygonGeometry;
32  aPolygonGeometry.Append( TGPoint( 15, 30 ) );
33  aPolygonGeometry.Append( TGPoint( 25, 100 ) );
34  aPolygonGeometry.Append( TGPoint( 150, 50 ) );
35  TPolygon* aPolygon = new TPolygon( aPolygonGeometry, polyBundle );
36  
37  TGPolygon aPolygonGeometry2;
38  aPolygonGeometry2.Append( TGPoint( 15, 170 ) );
39  aPolygonGeometry2.Append( TGPoint( 25, 110 ) );
40  aPolygonGeometry2.Append( TGPoint( 150, 60 ) );
41  TPolygon* aPolygon2 = new TPolygon( aPolygonGeometry2, polyBundle2 );
42  
43  TA8R8G8B8Image anRGBImage( TGPoint::kOrigin, 200, 200 );
44  TGrafPort* imagePort = anRGBImage.GetGrafPort();
45  imagePort->Draw( TGRect( 0, 0, 200, 200 ), redBundle ); 
46  
47  aPolygon->Draw( *imagePort );
48  aPolygon2->Draw( *imagePort );
49  
50  anRGBImage.Draw( thePort );

Lines 1 through 21: Create the attribute bundles.

polyBundle and polyBundle2 use a white fill color and a blue frame color. redBundle uses a red fill.
polyBundle uses full opacity (an opacity value of 1), polyBundle2 uses half opacity (an opacity value of .5), and redBundle uses full opacity (an opacity value of 1).

When used with compositing transfer modes, these opacity values control how the fill and frame colors of the polygons blend with the red fill color of the image. An opacity value of 1 means that the fill and frame colors in polyBundle completely overlay the red fill color of the image, and that the fill and frame colors in polyBundle2 blend with the underlying red as follows: .5 of the red is mixed with .5 of the white frame, and .5 of the blue fill.

Lines 24 through 31: Create and the transfer modes and adopt them to polyBundle and polyBundle2. If you do not specify a transfer mode, a source copy is used by default. This means that the white frame and blue fill of each polygon is copied over the red background. When you specify a transfer mode, the colors are blended according to how the transfer mode algorithm blends with the opacity value.

The TGrayInvertSrcTransferMode is used for polyBundle to invert the source colors from white frame and blue fill to black frame and gray fill. The opacity values on the white frame and blue fill are changed from 1 to 0.5.
TRGBInvertSrcTransferMode is used for polyBundle2 to invert the source colors. The inversion causes the white frame (1,1,1) to be changed to black (0, 0, 0), and the blue fill (0, 0, 1) to be changed to yellow (1, 1, 0).

To see first-hand how transfer modes and opacity values interrelate, you should experiment with this code by changing transfer modes and opacity values and viewing the output.

Lines 32 through 42: Create the polyline graphics from the polyline geometries and attribute bundles.

Line 44: Create an image graphic that is 200 world-coordinate units wide and high.

Line 45: Get the image port so that you can draw into it.

Line 46: Draw a rectangle into the image port that is the same size as the image and include the redFill bundle. If you do not draw the imagePort with a fill bundle, the fill color is black by default. An opacity value of 1 for the red fill color for the image makes the red completely overlay the default black color of the image. Smaller values cause the red to mix with the black according to the opacity value.

Lines 48 and 49: Draw the polygons into the image port.

Line 51: Draw the image.

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