Bottom edge detection for J curve (x=630 to 1040):
x=630: edge at y=1032 (v0=76, v1=33)
x=670: edge at y=1056 (v0=109, v1=35)
x=710: edge at y=1070 (v0=127, v1=45)
x=750: edge at y=1077 (v0=68, v1=26)
x=790: edge at y=1077 (v0=79, v1=28)
x=830: edge at y=1071 (v0=93, v1=47)
x=870: edge at y=1058 (v0=124, v1=53)
x=910: edge at y=1038 (v0=125, v1=44)
x=950: edge at y=1009 (v0=78, v1=43)
x=990: edge at y=965 (v0=84, v1=44)