得出梯度方向

Question

所以我有以下代碼：

-

(void) drawLinearGradient:(CGRect) rect 
{ 
    CGContextRef context = UIGraphicsGetCurrentContext(); 
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB(); 
    CGFloat locations[] = { 0.0, 0.3, 1.0 }; 

    CGColorRef grayColor = [UIColor colorWithRed:37/255.f green:37/255.f 
              blue:37/255.f alpha:1.0].CGColor; 
    CGColorRef blueColor = [UIColor colorWithRed:23.0/255.0 green:171.0/255.0 
              blue:219.0/255.0 alpha:1.0].CGColor; 

    NSArray *colors = [NSArray arrayWithObjects: (id) grayColor, (id) grayColor, (id) blueColor, nil]; 

    CGGradientRef gradient = CGGradientCreateWithColors(colorSpace, 
                 (CFArrayRef) colors, locations); 

    CGPoint startPoint = CGPointMake(CGRectGetMidX(rect), CGRectGetMinY(rect)); 
    CGPoint endPoint = CGPointMake(CGRectGetMidX(rect), CGRectGetMaxY(rect)); 

    CGContextSaveGState(context); 
    CGContextAddRect(context, rect); 
    CGContextClip(context); 
    CGContextDrawLinearGradient(context, gradient, startPoint, endPoint, 0); 
    CGContextRestoreGState(context); 

    CGGradientRelease(gradient); 
    CGColorSpaceRelease(colorSpace); 
} 

這樣做是繪製漸變從上到下，我怎樣才能使它所以它吸引從左至右？

Answer 1

更改這兩行：

CGPoint startPoint = CGPointMake(CGRectGetMidX(rect), CGRectGetMinY(rect)); 
CGPoint endPoint = CGPointMake(CGRectGetMidX(rect), CGRectGetMaxY(rect)); 

到：

CGPoint startPoint = CGPointMake(CGRectGetMinX(rect), CGRectGetMidY(rect)); 
CGPoint endPoint = CGPointMake(CGRectGetMaxX(rect), CGRectGetMidY(rect));