error 00865! ArcMap geoprocessing. Raster to Polygon

I am trying to write a python script to process image files into shapefiles and then to buffer these files with a 5 meter buffer. I first made the script in model builder in arcmap but I am trying to run it for multiple image files, all beginning with the letters LG. I keep getting the error 00865, which states that the input raster (image file) does not exist!! I have checked the folder a million times and it definitely does exist! Here is my code:

# Import system modules
import sys, string, os, arcgisscripting

# Create the Geoprocessor object
gp = arcgisscripting.create()

# Load required toolboxes...
gp.AddToolbox("C:/Program Files/ArcGIS/ArcToolbox/Toolboxes/Conversion Tools.tbx")
gp.AddToolbox("C:/Program Files/ArcGIS/ArcToolbox/Toolboxes/Analysis Tools.tbx")

# Script arguments...

folder = "D:\\J04-0083\\IMAGEFILES"
for root, dirs, filenames in os.walk(folder): # returms root, dirs, and files
    for filename in filenames:
        filename_split = os.path.splitext(filename) # filename and extensionname (extension in [1])
        filename_zero = filename_split[0]

        try:
            first_2_letters = filename_zero[0] + filename_zero[1]
        except:
            first_2_letters = "XX"

        if first_2_letters == "LG":
            Output_polygon_features = "D:\\J04-0083\\ShapeFiles.gdb\\" + "SH_" + filename + ".shp"

            # Process: Raster to Polygon...

            InRaster = filename_zero + ".png"
            gp.RasterToPolygon_conversion(InRaster, Output_polygon_features, "SIMPLIFY", "VALUE") # FILL IN THE CORRECT VALUES!

            Distance__value_or_field_ = "5 Meters"
            Raster_Buffer_shp = "D:\\J04-0083\\ShapeFiles.gdb\\" + "SB_" + filename + ".shp"
            # Process: Buffer...
            gp.Buffer_analysis(Output_polygon_features, Raster_Buffer_shp, Distance__value_or_field_, "FULL", "ROUND", "NONE", "")

Does anyone have any idea why it doesn't work? thank you!

Solution

I don't know where you're running the script from, but when you call gp.RasterToPolygon_conversion, you're only giving it the file name, not the full path. If the file's not in the working directory, it won't find it. Try replacing the line:

InRaster = filename_zero + ".png"

With:

InRaster = os.path.join(root, filename_zero + ".png")