针对不用layer的切图处理

如果要适配ios7的系统，要给一张图片切成一张圆形图，用layer的圆角发现程序很"卡"，所以如果可以，用“绘图”技术来解决问题，通过看视频，获取了信息，封装了一个工具分类

.h文件

/*  设置圆环切图

*  name:要切图的图片名

*  borderWidth: 被切掉的圆环的边框宽度

*  borderColor: 边框颜色

*/

+(instancetype)circleImageWithName:(NSString *)name borderWidth:(CGFloat)borderWidth borderColor:(UIColor *)borderColor;

/**

*  圆形图片

*/

-(UIImage *)circleImage;

.m文件

+(instancetype)circleImageWithName:(NSString *)name borderWidth:(CGFloat)borderWidth borderColor:(UIColor *)borderColor

{

//获得老图片

UIImage *oldimage = [UIImage imageNamed:name];

//开始画图上下文(由于外面要设计一个大圆环，所以这个小相对大一点了)

CGFloat imgW = oldimage.size.width + borderWidth;

CGFloat imgH = oldimage.size.height + borderWidth;

CGSize imgSize = CGSizeMake(imgW, imgH);

UIGraphicsBeginImageContextWithOptions(imgSize, NO, 0.0);

//获得上下文

CGContextRef ref = UIGraphicsGetCurrentContext();

//画外面的圆环

[borderColor set];

CGFloat bigRadius = imgW * 0.5;

CGFloat currentX = bigRadius;

CGFloat currentY = bigRadius;

CGContextAddArc(ref, currentX, currentY, bigRadius, 0, M_PI * 2, 0);

CGContextFillPath(ref);

//画里面的小圆

CGFloat smallRadius = bigRadius - borderWidth;

CGContextAddArc(ref, currentX, currentY, smallRadius, 0, M_PI * 2, 0);

//裁剪

CGContextClip(ref);

//画图

[oldimage drawInRect:CGRectMake(borderWidth, borderWidth, oldimage.size.width, oldimage.size.height)];

//取图

UIImage *newImg = UIGraphicsGetImageFromCurrentImageContext();

//结束上下文

UIGraphicsEndImageContext();

return newImg;

}

-(UIImage *)circleImage

{

//第二个参数填NO是透明

UIGraphicsBeginImageContextWithOptions(self.size, NO, 0.0);

//获得上下文

CGContextRef ctx = UIGraphicsGetCurrentContext();

//获得一个圆

CGRect rect = CGRectMake(0, 0, self.size.width, self.size.height);

CGContextAddEllipseInRect(ctx, rect);

//裁剪

CGContextClip(ctx);

//将图片画上去

[self drawInRect:rect];

UIImage *image = UIGraphicsGetImageFromCurrentImageContext();

UIGraphicsEndImageContext();

return image;

}