vc.tabBarItem.selectedImage = image;

UIButton *btn = [UIButton buttonWithType:UIButtonTypeSystem];
[btn setImage:image forState:UIControlStateNormal];

// 加载图片
UIImage *tempImage = [UIImage imageNamed:@"tabBar_essence_click_icon"];
// 产生一张不会进行自动渲染的图片
UIImage *selectedImage = [tempImage imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal];
vc.tabBarItem.selectedImage = selectedImage;

#import <UIKit/UIKit.h>
@interface UIImage (Image)
+ (UIImage *)imageOriginalWithName:(NSString *)imageName;
@end

#import "UIImage+Image.h"
@implementation UIImage (Image)
+ (UIImage *)imageOriginalWithName:(NSString *)imageName
{
    UIImage *image = [UIImage imageNamed:imageName];
    return [image imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal];
}
@end