绘制纹理

#define H_PATTERN_SIZE 16
#define V_PATTERN_SIZE 18
#define H_PSIZE 16
#define V_PSIZE 18

void MyDrawColoredPattern (void *info, CGContextRef myContext)
{
    CGFloat subunit = 5; // the pattern cell itself is 16 by 18
  
    CGRect  myRect1 = {{0,0}, {subunit, subunit}},
    myRect2 = {{subunit, subunit}, {subunit, subunit}},
    myRect3 = {{0,subunit}, {subunit, subunit}},
    myRect4 = {{subunit,0}, {subunit, subunit}};
  
    CGContextSetRGBFillColor (myContext, 0, 0, 1, 1);
    CGContextFillRect (myContext, myRect1);
    CGContextSetRGBFillColor (myContext, 0, 0.5, .4, 1);
    CGContextFillRect (myContext, myRect2);
    CGContextSetRGBFillColor (myContext, 0, 1, 0, 1);
    CGContextFillRect (myContext, myRect3);
    CGContextSetRGBFillColor (myContext, .5, 0, 1.5, 1);
    CGContextFillRect (myContext, myRect4);
}

void MyColoredPatternPainting (CGContextRef myContext,
                               CGRect rect)
{
    CGPatternRef    pattern;// 1
    CGColorSpaceRef patternSpace;// 2
    CGFloat        alpha = 1,// 3
    width, height;// 4
    staticconst    CGPatternCallbacks callbacks = {0, // 5
        &MyDrawColoredPattern,
        NULL};
  
    CGContextSaveGState (myContext);
  
//    CGContextTranslateCTM(myContext, rect.origin.x, rect.origin.y);
//    CGContextTranslateCTM(myContext, 0, rect.size.height);
//    CGContextScaleCTM(myContext, 1.0, -1.0);
//    CGContextTranslateCTM(myContext, -rect.origin.x, -rect.origin.y);
  
  
    patternSpace = CGColorSpaceCreatePattern (NULL);// 6
    CGContextSetFillColorSpace (myContext, patternSpace);// 7
    CGColorSpaceRelease (patternSpace);// 8
  
    pattern = CGPatternCreate (NULL, // 9
                               CGRectMake (0, 0, H_PSIZE, V_PSIZE),// 10
                               CGAffineTransformMake (1, 0, 0, 1, 0, 0),// 11
                               H_PATTERN_SIZE, // 12
                               V_PATTERN_SIZE, // 13
                               kCGPatternTilingConstantSpacing,// 14
                               true, // 15
                               &callbacks);// 16
  
    CGContextSetFillPattern (myContext, pattern, &alpha);// 17
    CGPatternRelease (pattern);// 18
    CGContextFillRect (myContext, rect);// 19
    CGContextRestoreGState (myContext);
}