added test.py and example image for manual testing

.gitignore

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+/target
+**/*.rs.bk
+Cargo.lock
+.idea/
+*.png
+*.ffindex

test.py

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+import vapoursynth as vs
+core = vs.core
+
+#black = core.std.BlankClip(format=vs.YUV444P8, width=1920, height=1080, color=[0, 128, 128])
+#white = core.std.BlankClip(black, color=[255, 128, 128])
+core.std.LoadPlugin('target/release/libadaptivegrain_rs.so')
+zweihu = core.ffms2.Source('1558625524644.jpg').resize.Point(format=vs.YUV444PS).std.PlaneStats() * 200
+#grained = white.std.PlaneStats().adg.Mask()
+grained = zweihu.adg.Mask()
+#grained = zweihu
+#grained = white.grain.Add(2, constant=True)
+#for i in range(len(grained)):
+#    grained.get_frame(i)
+#grained.resize.Bicubic(format=vs.RGB24, matrix_in_s='709').imwri.Write('png', 'grain%d.png').get_frame(0)
+grained.set_output()
+#zweihu.set_output()