Error while building GTK 2.6.8 "failed to load "./stock_about_16.png": Couldn't recognize the image file format"

[Gowri Kandasamy <sharmikg gmail com>]

I have installed libpng 1.2.8 . When I try to build GTK with this png 
library , I get the following error message.
"

Entering directory `/gtk+-2.6.8/gtk/stock-icons'
GDK_PIXBUF_MODULE_FILE=../../gdk-pixbuf/gdk-pixbuf.loaders../../gdk-pixbuf/gdk-pixbuf-csource
\
--raw --build-list stock_about_16 ./stock_about_16.png stock_about_24 
./stock_about_24.png stock_add_16 ./stock_add_16.png stock_add_24 
./stock_add_24.png stock_align_center_16 ./stock_align_center_16.png 
stock_align_center_24 ./stock_align_center_24.png stock_align_justify_16 
./stock_align_justify_16.png stock_align_justify_24 
./stock_align_justify_24.png stock_align_left_16 ./stock_align_left_16.png 
stock_align_left_24 ./stock_align_left_24.png stock_align_right_16 
./stock_align_right_16.png stock_align_right_24 ./stock_align_right_24.png 
stock_apply_20 ./stock_apply_20.png stock_cancel_20 ./stock_cancel_20.png 
stock_dnd_multiple_32 ./stock_dnd_multiple_32.png stock_bottom_16 
./stock_bottom_16.png stock_bottom_24 ./stock_bottom_24.png stock_cdrom_16 
./stock_cdrom_16.png stock_cdrom_24 ./stock_cdrom_24.png stock_clear_24 
./stock_clear_24.png stock_close_20 ./stock_close_20.png stock_close_24 
./stock_close_24.png stock_colorselector_24 ./stock_colorselector_24.png 
stock_color_picker_25 ./stock_color_picker_25.png > gtkstockpixbufs.h || \
( rm -f gtkstockpixbufs.h && false )
failed to load "./stock_about_16.png": Couldn't recognize the image file 
format for file './stock_about_16.png'


I have the png library installed in /opt/GTK+2.6/lib/libpng.sl
& the Makefile has LIBPNG = -L/opt/GTK+2.6/lib -lpng12 -lz -lm . But still 
it could not recognize the png file

Am I missing something ??

Gowri