Crash at usage of GaussianBlur with small images

[nbossard]

Hello, I have been facing an issue when using method GaussianBlur.

If used on images smaller than (around) 230 px of width the library will crash systematically with error like following:

Error: Output buffer gaussianblur is accessed at -384, which is before the min (0) in dimension 1
SIGABRT: abort
PC=0x7f896a72000b m=5 sigcode=18446744073709551610
signal arrived during cgo execution

goroutine 53 [syscall]:
runtime.cgocall(0xeaf440, 0xc00045b550)
        /usr/local/go/src/runtime/cgocall.go:157 +0x5c fp=0xc00045b528 sp=0xc00045b4f0 pc=0x41201c
github.com/octu0/blurry._Cfunc_libgaussianblur(0xc0002b6000, 0x27, 0x67, 0x43fa0000, 0xc000362000)
        _cgo_gotypes.go:651 +0x4c fp=0xc00045b550 sp=0xc00045b528 pc=0xe383ec
github.com/octu0/blurry.Gaussianblur(0xc000490300, 0x407f400000000000)
        /home/vagrant/go/pkg/mod/github.com/octu0/blurry@v1.20.1/gaussianblur.go:48 +0x9d fp=0xc00045b5a0 sp=0xc00045b550 pc=0xe3873d

Increasing the image width at 240px "solves" the issue. Seems that Boxblur is impacted too.

[nbossard]

Note too small height also makes crash, but can't find the formula, strange...
Globally if width*height<30K it crashes.