/// <summary>
/// Return the hash of the specified file, calculated using the specified hash algorithm.
/// </summary>
/// <param name="algorithm"></param>
/// <param name="filePath"></param>
/// <returns></returns>
public static ImageHash HashImage(HashAlgorithm algorithm, string filePath)
{
ImageHash hash;
switch (algorithm)
{
case HashAlgorithm.DCT:
ulong DCTHash;
NativeFunctions.ph_dct_imagehash(filePath, out DCTHash);
hash = new DCTHash(DCTHash);
break;
case HashAlgorithm.Radial:
NativeStructures.Digest digest;
NativeFunctions.ph_image_digest(filePath, 1, 1, out digest);
hash = new RadialHash(digest);
break;
case HashAlgorithm.MH:
int count;
IntPtr hashBytes = NativeFunctions.ph_mh_imagehash(filePath, out count);
hash = new MHHash(hashBytes, count);
break;
default:
throw new NotImplementedException();
}
return(hash);
}
/// <summary>
/// Compare two image hashes and return a value between 0 and 1.
/// 0 meaning the two hashes (and therefore underlying images) are the same,
/// and 1 meaning they are totally different.
/// </summary>
/// <param name="hash1"></param>
/// <param name="hash2"></param>
/// <returns></returns>
public static double CompareHashes(ImageHash hash1, ImageHash hash2)
{
if (hash1.Algorithm != hash2.Algorithm)
{
throw new ArgumentException("Both hashes must use the same algorithm!");
}
double result;
switch (hash1.Algorithm)
{
case HashAlgorithm.DCT:
int rawHammingResult =
NativeFunctions.ph_hamming_distance(((DCTHash)hash1).Hash, ((DCTHash)hash2).Hash);
result = NormalizeThreshold(HashAlgorithm.DCT, rawHammingResult);
break;
case HashAlgorithm.Radial:
NativeStructures.Digest digest1 = ((RadialHash)hash1).Digest;
NativeStructures.Digest digest2 = ((RadialHash)hash2).Digest;
double rawCrossCorrResult;
NativeFunctions.ph_crosscorr(ref digest1, ref digest2, out rawCrossCorrResult);
result = NormalizeThreshold(HashAlgorithm.Radial, rawCrossCorrResult);
break;
case HashAlgorithm.MH:
MHHash mhHash1 = (MHHash)hash1;
MHHash mhHash2 = (MHHash)hash2;
double rawHamming2Result =
NativeFunctions.ph_hammingdistance2(mhHash1.BytesPtr, mhHash1.ByteCount, mhHash2.BytesPtr, mhHash2.ByteCount);
result = NormalizeThreshold(HashAlgorithm.MH, rawHamming2Result);
break;
default:
throw new NotImplementedException();
}
return(result);
}
/// <summary>
/// Return the hash of the specified file, calculated using the specified hash algorithm.
/// </summary>
/// <param name="algorithm"></param>
/// <param name="filePath"></param>
/// <returns></returns>
public static ImageHash HashImage(HashAlgorithm algorithm, string filePath)
{
ImageHash hash;
switch (algorithm)
{
case HashAlgorithm.DCT:
ulong DCTHash;
NativeFunctions.ph_dct_imagehash(filePath, out DCTHash);
hash = new DCTHash(DCTHash);
break;
case HashAlgorithm.Radial:
NativeStructures.Digest digest;
NativeFunctions.ph_image_digest(filePath, 1, 1, out digest);
hash = new RadialHash(digest);
break;
case HashAlgorithm.MH:
int count;
IntPtr hashBytes = NativeFunctions.ph_mh_imagehash(filePath, out count);
hash = new MHHash(hashBytes, count);
break;
default:
throw new NotImplementedException();
}
return hash;
}
