把imageview 的 render as 设置成template image
或者重写一个ImageView的 category
@interface UIImageView (Utils)
- (void)setImageRenderingMode:(UIImageRenderingMode)renderMode;
@end
@implementation UIImageView (Utils)
- (void)setImageRenderingMode:(UIImageRenderingMode)renderMode
{
NSAssert(self.image, @"Image must be set before setting rendering mode");
self.image = [self.image imageWithRenderingMode:renderMode];
}