help with write_png error

Any thoughts on what is causing this error???

/bin64/ncarg64/lib/libncarg_gks.a(pixwrite_png.o): In function `write_png':
pixwrite_png.c:(.text+0x47d): undefined reference to `png_create_write_struct'
pixwrite_png.c:(.text+0x4a9): undefined reference to `png_create_info_struct'
pixwrite_png.c:(.text+0x4c4): undefined reference to `png_destroy_write_struct'
pixwrite_png.c:(.text+0x4f7): undefined reference to `png_destroy_write_struct'
pixwrite_png.c:(.text+0x523): undefined reference to `png_init_io'
pixwrite_png.c:(.text+0x561): undefined reference to `png_malloc'
pixwrite_png.c:(.text+0x5bb): undefined reference to `png_set_rows'
pixwrite_png.c:(.text+0x5fc): undefined reference to `png_set_IHDR'
pixwrite_png.c:(.text+0x62c): undefined reference to `png_write_png'
pixwrite_png.c:(.text+0x639): undefined reference to `png_destroy_write_struct'
collect2: ld returned 1 exit status
make: *** [a.out] Error 1

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