iphone reduce size(in bytes)of image with exif data

I have image which I have accessed from the image gallery. I want to store this image in the database and 开发者_如何学Pythonlater re size it and POST it to the server. Can any please tell me if I will loose the EXIF data if the image is compressed? My original image has the EXIF data. If the data is not lost. Please guide as to how I can compress and re size the image

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• Image Resizing

Lot of answers in this area, for example: The simplest way to resize an UIImage? or more details at https://stackoverflow.com/questions/1282830/uiimagepickercontroller-uiimage-memory-and-more

• Image Compression

You can use UIImageJPEGRepresentation C function, which is declared as ...

NSData * UIImageJPEGRepresentation (
   UIImage *image,
   CGFloat compressionQuality
);

... you can pass UIImage object and set compression quality within range 0.0 (maximum compression) to 1.0 (best quality).

• EXIF loss

See answers at https://stackoverflow.com/questions/1282830/uiimagepickercontroller-uiimage-memory-and-more

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if you want to compress image without losing exif, first you should get property of image,and the data UIImageJPEGRepresentation you get not contain exif.

1:getoritatinal Image data 2:compress providerData 3:wite exif to compress data

- (void)setImagePropertyWith:(ALAsset *)asset

 {
        //get full imageData
        ALAssetRepresentation * defaultRep = [asset defaultRepresentation];
        Byte *buffer = (Byte*)malloc(defaultRep.size);
        NSUInteger buffered = [defaultRep getBytes:buffer fromOffset:0.0 length:defaultRep.size error:nil];
        NSData * data = [NSData dataWithBytesNoCopy:buffer length:buffered freeWhenDone:YES];

        // compressData providerData 
        CGDataProviderRef jpegdata = CGDataProviderCreateWithCFData((CFDataRef)data);
        CGImageRef imageRef = CGImageCreateWithJPEGDataProvider(jpegdata, NULL, YES, kCGRenderingIntentDefault);
        UIImage * image = [UIImage imageWithCGImage:imageRef];
        NSData* finaldata = UIImageJPEGRepresentation(image, 0.5);

        //compressData with exif
        finaldata =  [self writeExif:(NSDictionary *)[self getPropertyOfdata:data] intoImage:finaldata];

    }
    - (CFDictionaryRef )getPropertyOfdata:(NSData *)data
    {
        CGImageSourceRef imageSource = CGImageSourceCreateWithData((CFDataRef)data, NULL);
        if (imageSource == NULL) {
            // Error loading image
            return nil;
        }
        NSDictionary *options = [NSDictionary dictionaryWithObjectsAndKeys:
                                 [NSNumber numberWithBool:NO], (NSString *)kCGImageSourceShouldCache,
                                 nil];
        CFDictionaryRef imageProperties = CGImageSourceCopyPropertiesAtIndex(imageSource, 0, (CFDictionaryRef)options);
        NSLog(@"ori:%@",imageProperties);
        return imageProperties;
    //    [self writeExif: (NSDictionary *)imageSource intoImageData:data];
    }