在Quartz 2D中使用pattern。

draw-arrow-with-pattern.mm

void drawStripes(void *info, CGContextRef con)
{
    // assume 4x4 cell
    CGContextSetFillColorWithColor(con, [[UIColor redColor] CGColor]);
    CGContextFillRect(con, CGRectMake(0, 2, 4, 2));
    CGContextSetFillColorWithColor(con, [[UIColor blueColor] CGColor]);
    CGContextFillRect(con, CGRectMake(0, 0, 4, 2));
}


// Only override drawRect: if you perform custom drawing.
// An empty implementation adversely affects performance during animation.
- (void)drawRect:(CGRect)rect
{
    // assume the background color is white
    
    CGContextRef con = UIGraphicsGetCurrentContext();
    CGContextSaveGState(con);
    
    // punch triangle hole in context clipping region
    CGContextMoveToPoint(con, 90, 100);
    CGContextAddLineToPoint(con, 100, 90);
    CGContextAddLineToPoint(con, 110, 100);
    CGContextClosePath(con);
    CGContextAddRect(con, CGContextGetClipBoundingBox(con));
    CGContextEOClip(con);
    
    // draw the vertical line, add its shape to the clipping region
    CGContextMoveToPoint(con, 100, 100);
    CGContextAddLineToPoint(con, 100, 19);
    CGContextSetLineWidth(con, 20);
    CGContextReplacePathWithStrokedPath(con);
    CGContextClip(con);
    
    // draw the gradient
    CGFloat locs[3] = {0., .5, 1.};
    CGFloat colors[12] = {
        .3, .3, .3, .8, // starting color
        .0,.0,.0,1.0,   // intermediate color
        .3, .3, .3, .8  // ending color
    };
    CGColorSpaceRef sp = CGColorSpaceCreateDeviceGray();
    CGGradientRef grad = CGGradientCreateWithColorComponents(sp, colors, locs, 3);
    CGContextDrawLinearGradient(con, grad, CGPointMake(89, 0), CGPointMake(111, 0), 0);
    CGColorSpaceRelease(sp);
    CGGradientRelease(grad);
    
    CGContextRestoreGState(con);
    
    // draw the triangle with pattern, the point of the arrow
    CGColorSpaceRef sp2 = CGColorSpaceCreatePattern(NULL);
    CGContextSetFillColorSpace(con, sp2);
    CGColorSpaceRelease(sp2);
    CGPatternCallbacks callback = {
        0, 
        &drawStripes,  // 绘制函数
        NULL           // 释放内存的函数
    };
    CGAffineTransform tr = CGAffineTransformIdentity;
    CGPatternRef patt = CGPatternCreate(NULL, 
                                        CGRectMake(0, 0, 4, 4),  // pattern cell's size
                                        tr, 
                                        4, 4,  // 相邻pattern的origin point的间隔
                                        kCGPatternTilingConstantSpacingMinimalDistortion, 
                                        true,  // if use color
                                        &callback); // 绘制函数
    CGFloat alph = 1.0;
    CGContextSetFillPattern(con, patt, &alph);
    CGPatternRelease(patt);
    CGContextMoveToPoint(con, 80, 25);
    CGContextAddLineToPoint(con, 100, 0);
    CGContextAddLineToPoint(con, 120, 25);
    CGContextFillPath(con);
}

和draw-arrow-with-gradient.mm唯一的差别是将CGContextSetFillColorWithColor(...)句替换成了和pattern有关的若干条语句。