pHash

Image hash based on pHash.

miyako/4d-plugin-phash

Attention If you create the PNG on Mac OS, make sure the “simple file” option is NOT used. Otherwise the hash value will be zero.

Compatibility note

Due to library update (0.9.6 to 1.0.0), function results are not the same as the old plugin.

Previous version was using the original 0.9.6 code for UNIX/MinGW.

Current version uses 1.0.0 for Mac and a pseudo 1.0.0 for Windows (based on 0.9.0 distributed with 1.0.0).

Windows 64-bit uses __popcnt64. __cpuid is not checked, since 64-bit version of 4D requires SSE4 anyway. 32-bit version uses classic emulation code.

ulong64 x = hash1^hash2;
#ifdef _WIN64
    return __popcnt64(x);
#else
  const ulong64 m1 = 0x5555555555555555ULL;
  const ulong64 m2 = 0x3333333333333333ULL;
  const ulong64 h01 = 0x0101010101010101ULL;
  const ulong64 m4 = 0x0f0f0f0f0f0f0f0fULL;
  x -= (x >> 1) & m1;
  x = (x & m2) + ((x >> 2) & m2);
  x = (x + (x >> 4)) & m4;
 
  return int((x * h01) >> 56);
#endif

status:=PH Compute DCT(file;hash)

wrapper of ph_dct_imagehash.

Attention contrary to header file description, status is 0 (not 1) for success and -1 for failure.

pcc:=PH Compare RADISH(file1;file2;sigma;gamma;n)

wrapper of ph_crosscorr.

pcc:=PH Compare MH(file1;file2;alpha;lvl)

wrapper of ph_hammingdistance2.

distance:=PH Compare DCT(hash1;hash2)