Create tiles for on Google Maps from PNG images

I have some PNG images in 2048, 4096, 8192 and 16384 pixel size to generate tiles for zoom level 3,4,5 and 6. My data are plotted in Mercator projection and centered over a particular area of clat and clon for example and limited by those coordinates : slat, nlat, elon, wlon

I have the

gdal and gdal2tiles.y

installed, i want to know how could i use gdal_tranlate to create the georeferencing images and tile them with gdal2tiles.py.

for you information when i call gdalinfo to know the information about my PNG images i get this

> Driver: PNG/Portable Network Graphics Files:
> tile_map_zoom3_1000_06.png Size is 2048, 2048 Coordinate System is `'
> Image Structure Metadata:   INTERLEAVE=PIXEL Corner Coordinates: Upper
> Left  (    0.0,    0.0) Lower Left  (    0.0, 2048.0) Upper Right (
> 2048.0,    0.0) Lower Right ( 2048.0, 2048.0) Center      ( 1024.0, 1024.0) Band 1 Block=2048x1 Type=Byte, ColorInterp=Red   Mask Flags: PER_DATASET ALPHA Band 2 Block=2048x1 Type=Byte, ColorInterp=Green  
> Mask Flags: PER_DATASET ALPHA Band 3 Block=2048x1 Type=Byte,
> ColorInterp=Blue   Mask Flags: PER_DATASET ALPHA Band 4 Block=2048x1
> Type=Byte, ColorInterp=Alpha