skr3dii-macbook:~/Desktop skr3dii$ gcc -c libpng-short-example.c 
libpng-short-example.c:18:17: error: png.h: No such file or directory
libpng-short-example.c:33: error: parse error before 'color_type'
libpng-short-example.c:33: warning: data definition has no type or storage class
libpng-short-example.c:34: error: parse error before 'bit_depth'
libpng-short-example.c:34: warning: data definition has no type or storage class
libpng-short-example.c:36: error: parse error before 'png_ptr'
libpng-short-example.c:36: warning: data definition has no type or storage class
libpng-short-example.c:37: error: parse error before 'info_ptr'
libpng-short-example.c:37: warning: data definition has no type or storage class
libpng-short-example.c:39: error: parse error before '*' token
libpng-short-example.c:39: warning: data definition has no type or storage class
libpng-short-example.c: In function 'read_png_file':
libpng-short-example.c:55: error: 'PNG_LIBPNG_VER_STRING' undeclared (first use in this function)
libpng-short-example.c:55: error: (Each undeclared identifier is reported only once
libpng-short-example.c:55: error: for each function it appears in.)
libpng-short-example.c:72: error: invalid type argument of '->'
libpng-short-example.c:73: error: invalid type argument of '->'
libpng-short-example.c:74: error: invalid type argument of '->'
libpng-short-example.c:75: error: invalid type argument of '->'
libpng-short-example.c:85: error: 'png_bytep' undeclared (first use in this function)
libpng-short-example.c:85: error: parse error before ')' token
libpng-short-example.c:87: error: 'png_byte' undeclared (first use in this function)
libpng-short-example.c:87: error: parse error before ')' token
libpng-short-example.c: In function 'write_png_file':
libpng-short-example.c:104: error: 'PNG_LIBPNG_VER_STRING' undeclared (first use in this function)
libpng-short-example.c:124: error: 'PNG_INTERLACE_NONE' undeclared (first use in this function)
libpng-short-example.c:125: error: 'PNG_COMPRESSION_TYPE_BASE' undeclared (first use in this function)
libpng-short-example.c:125: error: 'PNG_FILTER_TYPE_BASE' undeclared (first use in this function)
libpng-short-example.c:145: warning: passing argument 1 of 'free' makes pointer from integer without a cast
libpng-short-example.c: In function 'process_file':
libpng-short-example.c:156: error: invalid type argument of '->'
libpng-short-example.c:156: error: 'PNG_COLOR_TYPE_RGBA' undeclared (first use in this function)
libpng-short-example.c:157: error: invalid type argument of '->'
libpng-short-example.c:162: error: 'png_byte' undeclared (first use in this function)
libpng-short-example.c:162: error: parse error before 'tmp'
libpng-short-example.c:164: error: 'tmp' undeclared (first use in this function)
libpng-short-example.c:164: error: invalid type argument of 'unary *'
libpng-short-example.c:165: error: invalid type argument of 'unary *'
libpng-short-example.c:165: error: invalid type argument of 'unary *'
libpng-short-example.c:166: error: invalid type argument of 'unary *'