generate thumbnail

[storybehind]

Changes

• Generate thumbnail for given image. Decodes the given byte array to the image type. The thumbnail image is encoded in PNG format.
• Supported image format (decoding): jpeg, png and gif.
• Resampling filter should be either empty string (defaults to Lanczos) or one of the following: NearestNeighbor , Box , Linear , Hermite , MitchellNetravali , CatmullRom , BSpline , Gaussian , Bartlett , Lanczos , Hann , Hamming , Blackman , Welch , Cosine

Fixes

Tests

Tasks to complete before merging PR:

• [ ] Ensure system tests are passing. If not Run them manually to check for any regressions :clipboard:
• [ ] Do any new system tests need added to test this change? do any existing system tests need updated? If so create a PR at 0chain/system_test
• [ ] Merge your system tests PR to master AFTER merging this PR

Associated PRs (Link as appropriate):

• blobber:
• 0chain:
• system_test:
• zboxcli:
• zwalletcli:
• Other: ...