Comparing UIImage

Question

How can I compare an image to another one?

Thanks!

Answer 1

here 's code sample

-(NSMutableArray*)getImageBinary:(UIImage*)ImageToCompare
{
    int i = 0;    
    int step = 4;

    CGContextRef context = NULL;
    CGColorSpaceRef colorSpace;
    //void * bitmapData;
    //int bitmapByteCount;
    int bitmapBytesPerRow;

    // Get image width, height. We'll use the entire image.
    size_t pixelsWide = CGImageGetWidth(ImageToCompare.CGImage);
    size_t pixelsHigh = CGImageGetHeight(ImageToCompare.CGImage);

    // Declare the number of bytes per row. Each pixel in the bitmap in this
    // example is represented by 4 bytes; 8 bits each of red, green, blue, and
    // alpha.
    bitmapBytesPerRow = (pixelsWide * 4);
    NSMutableArray *firstImagearray=[[NSMutableArray alloc]init];

    //bitmapByteCount = (bitmapBytesPerRow * pixelsHigh);

    // Use the generic RGB color space.
    colorSpace = CGColorSpaceCreateDeviceRGB();

    if (colorSpace == NULL)
    {
        fprintf(stderr, "Error allocating color space\n");
        return nil;
    }

    // Allocate memory for image data. This is the destination in memory
    // where any drawing to the bitmap context will be rendered.
    //bitmapData = malloc( bitmapByteCount );
    //  if (bitmapData == NULL)
    //  {
    //      fprintf (stderr, "Memory not allocated!");
    //      CGColorSpaceRelease( colorSpace );
    //      return NULL;
    //  }

    // Create the bitmap context. We want pre-multiplied ARGB, 8-bits
    // per component. Regardless of what the source image format is
    // (CMYK, Grayscale, and so on) it will be converted over to the format
    // specified here by CGBitmapContextCreate.
    context = CGBitmapContextCreate (NULL,
                                     pixelsWide,
                                     pixelsHigh,
                                     8,      // bits        per component
                                     bitmapBytesPerRow,
                                     colorSpace,
                                     kCGImageAlphaPremultipliedFirst);

    if (context == NULL)
    {
        //free (bitmapData);
        fprintf (stderr, "Context not created!");
    }

    CGRect rect = {{0,0},{pixelsWide, pixelsHigh}};
    //
    // Draw the image to the bitmap context. Once we draw, the memory
    // allocated for the context for rendering will then contain the
    // raw image data in the specified color space.
    CGContextDrawImage(context, rect, ImageToCompare.CGImage);

    // Make sure and release colorspace before returning
    CGColorSpaceRelease( colorSpace );
    /////**********
    size_t _width = CGImageGetWidth(ImageToCompare.CGImage);
    size_t _height = CGImageGetHeight(ImageToCompare.CGImage);

    unsigned char* data = CGBitmapContextGetData (context);

    if (data != NULL) 
    {
        int max = _width * _height * 4;

        for (i = 0; i < max; i+=step)
        {
            [firstImagearray addObject:[NSNumber numberWithInt:data[i + 0]]];
            [firstImagearray addObject:[NSNumber numberWithInt:data[i + 1]]];
            [firstImagearray addObject:[NSNumber numberWithInt:data[i + 2]]];
            [firstImagearray addObject:[NSNumber numberWithInt:data[i + 3]]];     }
    }

    if (context == NULL)
        // error creating context
    return nil;


    //if (data) { free(data); }
    if (context) {
        CGContextRelease(context);
    }
    return firstImagearray;
}

-(BOOL)Compare:(UIImage*)ImageToCompare secondImage:(UIImage*)secondImage
{
    ImageToCompare=[ImageToCompare  scaleToSize:CGSizeMake(self.appdelegate.ScreenWidth,self.appdelegate.ScreenHeigth)];
    secondImage=[secondImage scaleToSize:CGSizeMake(self.appdelegate.ScreenWidth, self.appdelegate.ScreenHeigth)];

    NSArray *first=[[NSArray alloc] initWithArray:(NSArray *)[self    getImageBinary:ImageToCompare]];
    NSArray *second=[[NSArray alloc] initWithArray:(NSArray *)[self getImageBinary:secondImage]];

    for (int x=0; x