QuickTime 4 Reference

Creating a Vector Data Stream

Listing 2 shows how to create a vector data stream for a single path. The path has four on-curve points and two off-curve points. These points specify two curves and one straight line, as shown in Figure 58 . In addition to an atom for the path, the data stream includes an atom that specifies the fill type of subsequent paths in stream.

Listing 2 vector data stream for a single path



 
ComponentInstance vectorCodec;

Handle streamH;

Handle pathH;

gxPoint points[6];

Boolean isOnCurve[6];

int i;

long value;



/* open the vector codec component */

OpenADefaultComponent (decompressorComponentType,

                        kVectorCodecType, &vectorCodec);



/* create a new vector data stream */

CurveCreateVectorStream (vectorCodec, streamH);

value=gxOpenFrameFill;



/* add an atom to the vector data stream that specifies that 

   subsequent paths are to be drawn with open frame fill */

CurveAddAtomToVectorStream (ci, kCurveFillTypeAtom, sizeof(long),

                            &value, streamH);



/* specify the points for the path and whether each one is 

   on the path */

points[0].x = ff(50);

points[0].y = ff(100);

isOnCurve[0] = TRUE;

points[1].x = ff(0);

points[1].y = ff(75);

isOnCurve[1] = FALSE;

points[2].x = ff(50);

points[2].y = ff(50);

isOnCurve[2] = TRUE;

points[3].x = ff(150);

points[3].y = ff(50);

isOnCurve[3] = TRUE;

points[4].x = ff(200);

points[4].y = ff(75);

isOnCurve[4] = FALSE;

points[5].x = ff(150);

points[5].y = ff(100);

isOnCurve[5] = TRUE;



/* create the path and add the points to it */

CurveNewPath (vectorCodec, &pathH);

for (i = 0; i <= 5; i++)

    CurveInsertPointIntoPath (vectorCodec, &points[i], pathH,

                              1, i, isOnCurve[i]);



/* add the path to the vector data stream */

CurveAddPathAtomToVectorStream (vectorCodec, pathH, streamH);



/* mark the end of the vector data stream by adding a 

   kCurveEndAtom atom to the stream */

CurveAddZeroAtomToVectorStream (vectorCodec, streamH);



/* use the vector codec here to decompress and display the vector data */



/* dispose of stream and path handles when done */

DisposeHandle (streamH);

DisposeHandle (pathH);

Figure 58 A path with six points