截取当前屏幕

UIGraphicsBeginImageContextWithOptions(CGSizeMake(CGRectGetWidth(self.superview.frame), CGRectGetHeight(self.superview.frame)), NO, 1);
[self.superview drawViewHierarchyInRect:CGRectMake(0, 0, CGRectGetWidth(self.superview.frame), CGRectGetHeight(self.superview.frame)) afterScreenUpdates:NO];
UIImage *snapshot = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

选择本地图片

UIImagePickerController *imagePicker = [[UIImagePickerController alloc] init];
imagePicker.delegate = self;
imagePicker.sourceType = UIImagePickerControllerSourceTypePhotoLibrary;
imagePicker.modalTransitionStyle = UIModalTransitionStyleCoverVertical;
//        imagePicker.allowsEditing = YES;
[self presentViewController:imagePicker animated:YES completion:nil];

图片压缩

- (UIImage*)presentImageWithBigImg:(UIImage*)image
{
    NSData *imageData = UIImageJPEGRepresentation(image,0.001);
    UIImage *newImg = [UIImage imageWithData:imageData];
    if (newImg) {
        return newImg;
    }else{
        return image;
    }
}

iOS常用到的图片功能:截取当前屏幕/选择本地图片/图片压缩