IOS 绘制背景色渐变的矩形

<pre>

• (void)drawRect:(CGRect)rect {

CGFloat y = 0;
CGContextRef context = UIGraphicsGetCurrentContext(); //高需要变
[self _drawGradientColor:context
                    rect:CGRectMake(0, y, self.frame.size.width, incrementHeight)
                 options:kCGGradientDrawsAfterEndLocation
                  colors:self.colorsArray];
CGContextStrokePath(context);// 描线,即绘制形状
CGContextFillPath(context);// 填充形状内的颜色

}

/**
02

• 绘制背景色渐变的矩形，p_colors渐变颜色设置，集合中存储UIColor对象（创建Color时一定用三原色来创建）
  03
  **/

• (void)_drawGradientColor:(CGContextRef)p_context

                  rect:(CGRect)p_clipRect
  
               options:(CGGradientDrawingOptions)p_options
  
                colors:(NSArray *)p_colors {
  

  CGContextSaveGState(p_context);// 保持住现在的context

  CGContextClipToRect(p_context, p_clipRect);// 截取对应的context

  NSUInteger colorCount = p_colors.count;

  int numOfComponents = 4;

  CGColorSpaceRef rgb = CGColorSpaceCreateDeviceRGB();

  CGFloat colorComponents[colorCount * numOfComponents];

  for (int i = 0; i < colorCount; i++) {

    UIColor *color = p_colors[i];
    
    CGColorRef temcolorRef = color.CGColor;
    
    const CGFloat *components = CGColorGetComponents(temcolorRef);
    
    for (int j = 0; j < numOfComponents; ++j) {
        
        colorComponents[i * numOfComponents + j] = components[j];
        
    }
  

  }

  CGGradientRef gradient = CGGradientCreateWithColorComponents(rgb, colorComponents, NULL, colorCount);

  CGColorSpaceRelease(rgb);

  CGPoint startPoint = p_clipRect.origin;

  CGPoint endPoint = CGPointMake(CGRectGetMinX(p_clipRect), CGRectGetMaxY(p_clipRect));

  CGContextDrawLinearGradient(p_context, gradient, startPoint, endPoint, p_options);

  CGGradientRelease(gradient);

  CGContextRestoreGState(p_context);// 恢复到之前的context

}
</pre>

IOS 绘制背景色渐变的矩形