我认为@ChrisMiles是正确的,分段可能是单独绘制的。(我最初认为可以使用CGPatternRef进行操作,但您在模式绘制回调中没有访问CTM或路径端点。)
考虑到这一点,以下是一个极为简陋的草稿示例,说明如何开始这样的努力(单独填充各段)。请注意:
渐变颜色是猜测的
末端帽不存在,需要单独实现
一些锯齿效应仍然存在
没有太多关注性能
希望这至少可以让您开始工作(并解决一些解析几何问题)。
- (CGGradientRef)lineGradient
{
static CGGradientRef gradient = NULL;
if (gradient == NULL) {
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
CGColorRef white = [[UIColor colorWithWhite:1.f
alpha:0.7f] CGColor];
CGColorRef blue = [[UIColor colorWithRed:0.1f
green:0.2f
blue:1.f
alpha:0.7f] CGColor];
CGColorRef lightBlue = [[UIColor colorWithRed:0.4f
green:0.6f
blue:1.f
alpha:0.7f] CGColor];
CFMutableArrayRef colors = CFArrayCreateMutable(kCFAllocatorDefault,
8,
NULL);
CFArrayAppendValue(colors, blue);
CFArrayAppendValue(colors, blue);
CFArrayAppendValue(colors, white);
CFArrayAppendValue(colors, white);
CFArrayAppendValue(colors, lightBlue);
CFArrayAppendValue(colors, lightBlue);
CFArrayAppendValue(colors, blue);
CFArrayAppendValue(colors, blue);
CGFloat locations[8] = {0.f, 0.08f, 0.14f, 0.21f, 0.29f, 0.86f, 0.93f, 1.f};
gradient = CGGradientCreateWithColors(colorSpace,
colors,
locations);
CFRelease(colors);
CGColorSpaceRelease(colorSpace);
}
return gradient;
}
- (void)drawRect:(CGRect)rect
{
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSaveGState(context);
CGContextSetAllowsAntialiasing(context, YES);
CGContextSetShouldAntialias(context, YES);
[[UIColor whiteColor] setFill];
UIRectFill(rect);
CGFloat strokeWidth = 10.f;
CGContextSetLineWidth(context, strokeWidth);
CGGradientRef gradient = [self lineGradient];
CGPoint points[9] = {
CGPointMake(10.f, 25.f),
CGPointMake(100.f, 100.f),
CGPointMake(100.f, 150.f),
CGPointMake(22.f, 300.f),
CGPointMake(230.f, 400.f),
CGPointMake(230.f, 200.f),
CGPointMake(300.f, 200.f),
CGPointMake(310.f, 160.f),
CGPointMake(280.f, 100.f)
};
for (NSUInteger i = 1; i < 9; i++) {
CGPoint start = points[i - 1];
CGPoint end = points[i];
CGFloat dy = end.y - start.y;
CGFloat dx = end.x - start.x;
CGFloat xOffset, yOffset;
if (dx == 0) {
xOffset = 0.5 * strokeWidth;
yOffset = 0.f;
if (dy < 0) {
xOffset *= -1;
}
}
else if (dy == 0) {
xOffset = 0.f;
yOffset = 0.5 * strokeWidth;
}
else {
CGFloat gradientSlope = - dx / dy;
xOffset = 0.5 * strokeWidth / sqrt(1 + gradientSlope * gradientSlope);
yOffset = 0.5 * strokeWidth / sqrt(1 + 1 / (gradientSlope * gradientSlope));
if (dx < 0 && dy > 0) {
yOffset *= -1;
}
else if (dx > 0 && dy < 0) {
xOffset *= -1;
}
else if (dx < 0 && dy < 0) {
yOffset *= -1;
xOffset *= -1;
}
else {
}
}
CGAffineTransform startTransform = CGAffineTransformMakeTranslation(-xOffset, yOffset);
CGAffineTransform endTransform = CGAffineTransformMakeTranslation(xOffset, -yOffset);
CGPoint gradientStart = CGPointApplyAffineTransform(start, startTransform);
CGPoint gradientEnd = CGPointApplyAffineTransform(start, endTransform);
CGContextSaveGState(context);
CGContextMoveToPoint(context, start.x, start.y);
CGContextAddLineToPoint(context, end.x, end.y);
CGContextReplacePathWithStrokedPath(context);
CGContextClip(context);
CGContextDrawLinearGradient(context,
gradient,
gradientStart,
gradientEnd,
kCGGradientDrawsAfterEndLocation | kCGGradientDrawsBeforeStartLocation);
CGContextRestoreGState(context);
}
CGContextRestoreGState(context);
}