+ (NSImage *)imageResize:(NSImage*)anImage newSize:(NSSize)newSize {
    NSImage *sourceImage = anImage;
    // Report an error if the source isn't a valid image
    if (!sourceImage.valid){
        NSLog(@"Invalid Image");
    } else {
        NSImage *smallImage = [[NSImage alloc] initWithSize: newSize];
        [smallImage lockFocus];
        sourceImage.size = newSize;
        [NSGraphicsContext currentContext].imageInterpolation = NSImageInterpolationHigh;
        [sourceImage drawAtPoint:NSZeroPoint fromRect:CGRectMake(0, 0, newSize.width, newSize.height) operation:NSCompositeCopy fraction:1.0];
        [smallImage unlockFocus];
        return smallImage;
    }
    return nil;
}

+ (NSDictionary*)_compressedInfoBylubanAlgorithm:(NSData*)imageData calibrateSize:(int)calibrateSize{
    CGSize imageSize = [[self class] getImageSizeWithData:imageData];
    int width = imageSize.width;
    int height = imageSize.height;
    
    // 缩略图尺寸设为2的倍数,为后面的缩放做准备
    int thumbW = width % 2 == 1 ? width + 1 : width;
    int thumbH = height % 2 == 1 ? height + 1 : height;
    
    // width = 短
    // height = 长
    BOOL exchanged = NO;
    if (thumbW > thumbH) {
        width = thumbH;
        height = thumbW;
        exchanged = YES;
    }
    
    double scale = ((double) width / height);
    double size = 0;
    
    if (scale <= 1 && scale > 0.5625) {
        if (height < 1664) {
            if (imageData.length / 1024 < 150) {
                size = imageData.length/1024;
            }
            else{
                size = (width * height) / pow(1664, 2) * 150;
                size = size < 60 ? 60 : size;
            }
        } else if (height >= 1664 && height < 4990) {
            thumbW = width / 2;
            thumbH = height / 2;
            size = (thumbW * thumbH) / pow(2495, 2) * 300;
            size = size < 60 ? 60 : size;
        } else if (height >= 4990 && height < 10240) {
            thumbW = width / 4;
            thumbH = height / 4;
            size = (thumbW * thumbH) / pow(2560, 2) * 300;
            size = size < 100 ? 100 : size;
        } else {
            int multiple = height / 1280 == 0 ? 1 : height / 1280;
            thumbW = width / multiple;
            thumbH = height / multiple;
            size = (thumbW * thumbH) / pow(2560, 2) * 300;
            size = size < 100 ? 100 : size;
        }
    } else if (scale <= 0.5625 && scale > 0.5) {
        if (height < 1280 && imageData.length / 1024 < 200) {
            size = imageData.length/1024;
        }
        else{
            int multiple = height / 1280 == 0 ? 1 : height / 1280;
            thumbW = width / multiple;
            thumbH = height / multiple;
            size = (thumbW * thumbH) / (1440.0 * 2560.0) * 200;
            size = size < 100 ? 100 : size;
        }
    } else {
        int multiple = (int) ceil(height / (1280.0 / scale));
        thumbW = width / multiple;
        thumbH = height / multiple;
        size = ((thumbW * thumbH) / (1280.0 * (1280 / scale))) * 500;
        size = size < 100 ? 100 : size;
    }
    
    if (exchanged) {
        thumbW = thumbW + thumbH;
        thumbH = thumbW - thumbH;
        thumbW = thumbW - thumbH;
    }
    
    //不能超过服务端限制 1M
    size = size * 1024;
    size = MAX(size, calibrateSize);// size < calibrateSize(用于降低压缩的程度，提升压缩速度) < M1
    size = MIN(size, imageData.length); //不超过初始大小
    size = MIN(size, M1);
    
    NSDictionary* compressedInfo = @{@"size":@(size),
                                     @"scale":@(scale),
                                     @"thumbW":@(thumbW),
                                     @"thumbH":@(thumbH)};
    return compressedInfo;
}

+ (NSData *)_thumbnailImageDataWithImageData:(NSData *)imageData
                                maxPixelSize:(CGFloat)maxPixelSize
                                     quality:(CGFloat)quality {
    CGImageSourceRef imageSource = CGImageSourceCreateWithData((CFDataRef) imageData, NULL);
    NSDictionary *imageOptions = @{
                                   (__bridge NSString *) kCGImageSourceCreateThumbnailFromImageAlways : @YES,
                                   (__bridge NSString *) kCGImageSourceThumbnailMaxPixelSize : [NSNumber numberWithUnsignedInteger:maxPixelSize],
                                   (__bridge NSString *) kCGImageSourceCreateThumbnailWithTransform : @YES,
                                   };
    
    CGImageRef imageRef = CGImageSourceCreateThumbnailAtIndex(imageSource,
                                                              0,
                                                              (__bridge CFDictionaryRef) imageOptions);
    // release
    if (imageSource) {
        CFRelease(imageSource);
    }
    
    NSMutableData *thumbnailImageData = [[NSMutableData alloc] init];
    CGImageDestinationRef destRef = CGImageDestinationCreateWithData((__bridge CFMutableDataRef) thumbnailImageData,
                                                                     kUTTypeJPEG,
                                                                     1,
                                                                     NULL);
    
    NSDictionary *imageAddOptions = @{
                                      (__bridge NSString *) kCGImageDestinationLossyCompressionQuality : [NSNumber numberWithFloat:quality],
                                      //(NSString *)kCGImageDestinationOptimizeColorForSharing:@(YES) //仅支持10.12及其以上
                                      };
    
    CGImageDestinationAddImage(destRef,
                               imageRef,
                               (__bridge CFDictionaryRef) imageAddOptions);
    CGImageDestinationFinalize(destRef);
    // release
    if (imageRef) {
        CFRelease(imageRef);
    }
    // release
    if (destRef) {
        CFRelease(destRef);
    }
    return thumbnailImageData;
}

NSBitmapImageRep *imageRep = [NSBitmapImageRep imageRepWithData:data];
if (imgType == ImageSuffixType_png) {
    data = [imageRep representationUsingType:NSPNGFileType properties:@{}];
}
else {
     NSDictionary* imageProps = @{NSImageCompressionFactor: @(compression)};
    data = [imageRep representationUsingType:NSJPEGFileType properties:imageProps];
}

+ (NSData*) convertProfileImageTosRGB:(NSImage*)image{
    if(image != nil) {
        
        CGImageRef cgImage = [ImageHelper newCGImageRefFromNSImage:image];
        NSBitmapImageRep *imageRep = [[NSBitmapImageRep alloc] initWithCGImage:cgImage];
        CGImageRelease(cgImage);
        
       if(![imageRep.colorSpace.localizedName containsString:@"RGB"]){
            imageRep = [imageRep bitmapImageRepByConvertingToColorSpace:[NSColorSpace sRGBColorSpace]renderingIntent:NSColorRenderingIntentDefault];
            [imageRep setProperty:NSImageColorSyncProfileData withValue:nil];
            
            NSData* imageData = [NSBitmapImageRep representationOfImageRepsInArray:@[imageRep] usingType:NSJPEGFileType properties:@{NSImageCompressionFactor:@(1)}];
            
            return imageData;
        }
        
    }
    
    return nil;
}

+(NSSize)getImageSizeWithData:(NSData *)imageData{
    NSBitmapImageRep *rep = [NSBitmapImageRep imageRepWithData:imageData];
    return NSMakeSize(rep.pixelsWide, rep.pixelsHigh);
}
NSImage size method return size in points. To get size represented in pixels you need inspect NSImage.representations property that contains an array of NSImageRep objects with pixelWide/pixelHigh properties and simple change size NSImage object:
NSImage size method returns size information that is screen resolution dependent. To get the size represented in the actual file image you need to use an NSImageRep. You can get an NSImageRepfrom an NSImage using the representations method. Alternatively you can create a NSBitmapImageRep subclass instance directly like this:
NSArray * imageReps = [NSBitmapImageRep imageRepsWithContentsOfFile:@"<path to image>"];
NSInteger width = 0;
NSInteger height = 0;
for (NSImageRep * imageRep in imageReps) {
    if ([imageRep pixelsWide] > width) width = [imageRep pixelsWide];  
    if ([imageRep pixelsHigh] > height) height = [imageRep pixelsHigh];  
}
NSLog(@"Width from NSBitmapImageRep: %f",(CGFloat)width);
NSLog(@"Height from NSBitmapImageRep: %f",(CGFloat)height);