three.js/utils/exporters/convert_obj_threejs.py

"""Convert Wavefront OBJ / MTL files into Three.js

-------------------------
How to use this converter
-------------------------

python convert_obj_threejs.py -i filename.obj -o filename.js [-a center|top|bottom]

Note: by default, model is centered (middle of bounding box goes to 0,0,0).
 
--------------------------------------------------
How to use generated JS file in your HTML document
--------------------------------------------------

    <script type="text/javascript" src="Three.js"></script>
    <script type="text/javascript" src="ModelName.js"></script>
    
    ...
    
    <script type="text/javascript">
        ...
        
        var normalizeUVsFlag = 1; // set to 1 if canvas render has missing materials
        var geometry = new ModelName( path_to_textures );
        var mesh = new THREE.Mesh( geometry, geometry.materials, normalizeUVsFlag );
        
        ...
    </script>
    
-------------------------------------
Parsers based on formats descriptions
-------------------------------------

    http://en.wikipedia.org/wiki/Obj
    http://en.wikipedia.org/wiki/Material_Template_Library
    
-------------------
Current limitations
-------------------

    - for the moment, only diffuse color and texture are used 
      (will need to extend shaders / renderers / materials in Three)
     
    - models cannot have more than 65,536 vertices
      (this comes from WebGL using just 16-bit indices,
       could be worked around by expanding indexed
       faces into full vertex definitions)
       
    - texture coordinates can be wrong in canvas renderer
      (there is crude normalization, but it doesn't
       work for all cases)
       
    - everything is using smoothing
      (if you want flat shading for whole mesh, 
       don't export normals, then Three will 
       compute own normals)

---------------------------------------------- 
How to get proper OBJ + MTL files with Blender
----------------------------------------------

    0. Remove default cube (press DEL and ENTER)
    
    1. Import / create model
    
    2. Select all meshes (Select -> Select All by Type -> Mesh)
    
    3. Export to OBJ (File -> Export -> Wavefront .obj) [*]
        - enable following options in exporter
            Material Groups
            Rotate X90
            Apply Modifiers
            High Quality Normals
            Copy Images
            Selection Only
            Objects as OBJ Objects
            UVs
            Normals
            Materials
            Edges
            
        - select empty folder
        - give your exported file name with "obj" extension
        - click on "Export OBJ" button
        
    4. Your model is now all files in this folder (OBJ, MTL, number of images)
        - this converter assumes all files staying in the same folder,
          (OBJ / MTL files use relative paths)
          
        - for WebGL, textures must be power of 2 sized

    [*] If OBJ export fails (Blender 2.54 beta), patch your Blender installation 
        following instructions here:
            
            http://www.blendernation.com/2010/09/12/blender-2-54-beta-released/
            
------           
Author 
------
AlteredQualia http://alteredqualia.com            

"""

import fileinput
import operator
import random
import os.path
import getopt
import sys

# #####################################################
# Configuration
# #####################################################
ALIGN = "center" # center bottom top none

# default colors for debugging (each material gets one distinct color): 
# white, red, green, blue, yellow, cyan, magenta
COLORS = [0xffeeeeee, 0xffee0000, 0xff00ee00, 0xff0000ee, 0xffeeee00, 0xff00eeee, 0xffee00ee]

# #####################################################
# Templates
# #####################################################
TEMPLATE_FILE = u"""\
// Converted from: %(fname)s
//  vertices: %(nvertex)d
//  faces: %(nface)d 
//  materials: %(nmaterial)d
//
//  This file was generated by "convert_obj_treejs.py"

var %(name)s = function ( urlbase ) {
    var scope = this;

    THREE.Geometry.call(this);

    var materials = [%(materials)s];

    init_materials();
    
    var normals = [%(normals)s];

%(vertices)s

%(uvs)s

%(faces)s

    this.computeCentroids();
    this.computeNormals();
    
    function material_color( mi ) {
        var m = materials[mi];
        if( m.col_diffuse )
            return (m.col_diffuse[0]*255 << 16) + (m.col_diffuse[1]*255 << 8) + m.col_diffuse[2]*255;
        else if ( m.a_dbg_color )
            return  m.a_dbg_color;
        else 
            return 0xffeeeeee;
    }
    
    function v( x, y, z ) {
        scope.vertices.push( new THREE.Vertex( new THREE.Vector3( x, y, z ) ) );
    }

    function f3( a, b, c, material ) {
        var color = material_color(material);
        scope.faces.push( new THREE.Face3( a, b, c, null, new THREE.Color(color), material ) );
    }

    function f4( a, b, c, d, material ) {
        var color = material_color(material);
        scope.faces.push( new THREE.Face4( a, b, c, d, null, new THREE.Color(color), material ) );
    }

    function f3n( a, b, c, material, n1, n2, n3 ) {
        var color = material_color(material);
        var n1x = normals[n1][0];
        var n1y = normals[n1][1];
        var n1z = normals[n1][2];
        var n2x = normals[n2][0];
        var n2y = normals[n2][1];
        var n2z = normals[n2][2];
        var n3x = normals[n3][0];
        var n3y = normals[n3][1];
        var n3z = normals[n3][2];
        scope.faces.push( new THREE.Face3( a, b, c, 
                          [new THREE.Vector3( n1x, n1y, n1z ), new THREE.Vector3( n2x, n2y, n2z ), new THREE.Vector3( n3x, n3y, n3z )], 
                          new THREE.Color(color), material ) );
    }

    function f4n( a, b, c, d, material, n1, n2, n3, n4 ) {
        var color = material_color(material);
        var n1x = normals[n1][0];
        var n1y = normals[n1][1];
        var n1z = normals[n1][2];
        var n2x = normals[n2][0];
        var n2y = normals[n2][1];
        var n2z = normals[n2][2];
        var n3x = normals[n3][0];
        var n3y = normals[n3][1];
        var n3z = normals[n3][2];
        var n4x = normals[n4][0];
        var n4y = normals[n4][1];
        var n4z = normals[n4][2];
        scope.faces.push( new THREE.Face4( a, b, c, d,
                          [new THREE.Vector3( n1x, n1y, n1z ), new THREE.Vector3( n2x, n2y, n2z ), new THREE.Vector3( n3x, n3y, n3z ), new THREE.Vector3( n4x, n4y, n4z )], 
                          new THREE.Color(color), material ) );
    }

    function uv( u1, v1, u2, v2, u3, v3, u4, v4 ) {
        var uv = [];
        uv.push( new THREE.UV( u1, v1 ) );
        uv.push( new THREE.UV( u2, v2 ) );
        uv.push( new THREE.UV( u3, v3 ) );
        if ( u4 && v4 ) uv.push( new THREE.UV( u4, v4 ) );
        scope.uvs.push( uv );
    }

    function init_materials() {
        scope.materials = [];
        for(var i=0; i<materials.length; ++i) {
            scope.materials[i] = create_material( materials[i], urlbase );
        }
    }
    
    function is_pow2( n ) {
        var l = Math.log(n) / Math.LN2;
        return Math.floor(l) == l;
    }
    
    function nearest_pow2(n) {
        var l = Math.log(n) / Math.LN2;
        return Math.pow( 2, Math.round(l) );
    }
    
    function create_material( m ) {
        var material;
        
        if( m.map_diffuse && urlbase ) {
            var texture = document.createElement( 'canvas' );
            
            material = new THREE.MeshBitmapUVMappingMaterial( texture );
            var image = new Image();
            
            image.onload = function () {
                
                if ( !is_pow2(this.width) || !is_pow2(this.height) ) {
                
                    var w = nearest_pow2( this.width );
                    var h = nearest_pow2( this.height );
                    material.bitmap.width = w;
                    material.bitmap.height = h;
                    material.bitmap.getContext("2d").drawImage( this, 0, 0, w, h );
                }
                else {
                    material.bitmap = this;
                }
                material.loaded = 1;
                
            };
            image.src = urlbase + "/" + m.map_diffuse;
        }
        else if( m.col_diffuse ) {
            var color = (m.col_diffuse[0]*255 << 16) + (m.col_diffuse[1]*255 << 8) + m.col_diffuse[2]*255;
            material = new THREE.MeshColorFillMaterial( color, m.transparency );
        }
        else if( m.a_dbg_color ) {
            material = new THREE.MeshColorFillMaterial( m.a_dbg_color );
        }
        else {
            material = new THREE.MeshFaceColorFillMaterial( );
        }

        return material;
    }
}

%(name)s.prototype = new THREE.Geometry();
%(name)s.prototype.constructor = %(name)s;
"""

TEMPLATE_VERTEX = "\tv(%f,%f,%f);"

TEMPLATE_UV3 = "\tuv(%f,%f,%f,%f,%f,%f);"
TEMPLATE_UV4 = "\tuv(%f,%f,%f,%f,%f,%f,%f,%f);"

TEMPLATE_FACE3  = "\tf3(%d,%d,%d,%d);"
TEMPLATE_FACE4  = "\tf4(%d,%d,%d,%d,%d);"

TEMPLATE_FACE3N  = "\tf3n(%d,%d,%d, %d, %d,%d,%d);"
TEMPLATE_FACE4N  = "\tf4n(%d,%d,%d,%d, %d, %d,%d,%d,%d);"

TEMPLATE_N = "[%f,%f,%f]"

# #####################################################
# Utils
# #####################################################
def file_exists(filename):
    """Return true if file exists and is accessible for reading.
    
    Should be safer than just testing for existence due to links and 
    permissions magic on Unix filesystems.
    
    @rtype: boolean
    """
    
    try:
        f = open(filename, 'r')
        f.close()
        return True
    except IOError:
        return False

    
def get_name(fname):
    """Create model name based of filename ("path/fname.js" -> "Fname").
    """
    
    return os.path.basename(fname).split(".")[0].capitalize()
  
def bbox(vertices):
    """Compute bounding box of vertex array.
    """
    
    if len(vertices)>0:
        minx = maxx = vertices[0][0]
        miny = maxy = vertices[0][1]
        minz = maxz = vertices[0][2]
        
        for v in vertices[1:]:
            if v[0]<minx:
                minx = v[0]
            elif v[0]>maxx:
                maxx = v[0]
            
            if v[1]<miny:
                miny = v[1]
            elif v[1]>maxy:
                maxy = v[1]

            if v[2]<minz:
                minz = v[2]
            elif v[2]>maxz:
                maxz = v[2]

        return { 'x':[minx,maxx], 'y':[miny,maxy], 'z':[minz,maxz] }
    
    else:
        return { 'x':[0,0], 'y':[0,0], 'z':[0,0] }

def translate(vertices, t):
    """Translate array of vertices by vector t.
    """
    
    for i in xrange(len(vertices)):
        vertices[i][0] += t[0]
        vertices[i][1] += t[1]
        vertices[i][2] += t[2]
        
def center(vertices):
    """Center model (middle of bounding box).
    """
    
    bb = bbox(vertices)
    
    cx = bb['x'][0] + (bb['x'][1] - bb['x'][0])/2.0
    cy = bb['y'][0] + (bb['y'][1] - bb['y'][0])/2.0
    cz = bb['z'][0] + (bb['z'][1] - bb['z'][0])/2.0
    
    translate(vertices, [-cx,-cy,-cz])

def top(vertices):
    """Align top of the model with the floor (Y-axis) and center it around X and Z.
    """
    
    bb = bbox(vertices)
    
    cx = bb['x'][0] + (bb['x'][1] - bb['x'][0])/2.0
    cy = bb['y'][1]
    cz = bb['z'][0] + (bb['z'][1] - bb['z'][0])/2.0
    
    translate(vertices, [-cx,-cy,-cz])
    
def bottom(vertices):
    """Align bottom of the model with the floor (Y-axis) and center it around X and Z.
    """
    
    bb = bbox(vertices)
    
    cx = bb['x'][0] + (bb['x'][1] - bb['x'][0])/2.0
    cy = bb['y'][0] 
    cz = bb['z'][0] + (bb['z'][1] - bb['z'][0])/2.0
    
    translate(vertices, [-cx,cy,-cz])

def normalize(v):
    """Normalize 3d vector"""
    
    l = math.sqrt(v[0]*v[0] + v[1]*v[1] + v[2]*v[2])
    v[0] /= l
    v[1] /= l
    v[2] /= l

# #####################################################
# MTL parser
# #####################################################
def parse_mtl(fname):
    """Parse MTL file.
    """
    
    materials = {}
    
    for line in fileinput.input(fname):
        chunks = line.split()
        if len(chunks) > 0:
            
            # Material start
            # newmtl identifier
            if chunks[0] == "newmtl" and len(chunks) == 2:
                identifier = chunks[1]
                if not identifier in materials:
                    materials[identifier] = {}

            # Diffuse color
            # Kd 1.000 1.000 1.000
            if chunks[0] == "Kd" and len(chunks) == 4:                
                materials[identifier]["col_diffuse"] = [float(chunks[1]), float(chunks[2]), float(chunks[3])]

            # Ambient color
            # Ka 1.000 1.000 1.000
            if chunks[0] == "Ka" and len(chunks) == 4:                
                materials[identifier]["col_ambient"] = [float(chunks[1]), float(chunks[2]), float(chunks[3])]

            # Specular color
            # Ks 1.000 1.000 1.000
            if chunks[0] == "Ks" and len(chunks) == 4:                
                materials[identifier]["col_specular"] = [float(chunks[1]), float(chunks[2]), float(chunks[3])]

            # Specular coefficient
            # Ns 154.000
            if chunks[0] == "Ns" and len(chunks) == 2:                
                materials[identifier]["specular_coef"] = float(chunks[1])

            # Transparency
            # Tr 0.9 or d 0.9
            if (chunks[0] == "Tr" or chunks[0] == "d") and len(chunks) == 2:                
                materials[identifier]["transparency"] = float(chunks[1])

            # Optical density
            # Ni 1.0
            if chunks[0] == "Ni" and len(chunks) == 2:                
                materials[identifier]["optical_density"] = float(chunks[1])

            # Diffuse texture
            # map_Kd texture_diffuse.jpg
            if chunks[0] == "map_Kd" and len(chunks) == 2:                
                materials[identifier]["map_diffuse"] = chunks[1]

            # Ambient texture
            # map_Ka texture_ambient.jpg
            if chunks[0] == "map_Ka" and len(chunks) == 2:
                materials[identifier]["map_ambient"] = chunks[1]

            # Specular texture
            # map_Ks texture_specular.jpg
            if chunks[0] == "map_Ks" and len(chunks) == 2:
                materials[identifier]["map_specular"] = chunks[1]

            # Alpha texture
            # map_d texture_alpha.png
            if chunks[0] == "map_d" and len(chunks) == 2:
                materials[identifier]["map_alpha"] = chunks[1]

            # Bump texture
            # map_bump texture_bump.jpg or bump texture_bump.jpg
            if (chunks[0] == "map_bump" or chunks[0] == "bump") and len(chunks) == 2:
                materials[identifier]["map_bump"] = chunks[1]

            # Illumination
            # illum 2
            #
            # 0. Color on and Ambient off
            # 1. Color on and Ambient on
            # 2. Highlight on
            # 3. Reflection on and Ray trace on
            # 4. Transparency: Glass on, Reflection: Ray trace on
            # 5. Reflection: Fresnel on and Ray trace on
            # 6. Transparency: Refraction on, Reflection: Fresnel off and Ray trace on
            # 7. Transparency: Refraction on, Reflection: Fresnel on and Ray trace on
            # 8. Reflection on and Ray trace off
            # 9. Transparency: Glass on, Reflection: Ray trace off
            # 10. Casts shadows onto invisible surfaces
            if chunks[0] == "illum" and len(chunks) == 2:
                materials[identifier]["illumination"] = int(chunks[1])

    return materials
    
# #####################################################
# OBJ parser
# #####################################################
def parse_vertex(text):
    """Parse text chunk specifying single vertex.
    
    Possible formats:
        vertex index
        vertex index / texture index
        vertex index / texture index / normal index
        vertex index / / normal index
    """
    
    v = 0
    t = 0
    n = 0
    
    chunks = text.split("/")
    
    v = int(chunks[0])
    if len(chunks) > 1:
        if chunks[1]:
            t = int(chunks[1])
    if len(chunks) > 2:
        if chunks[2]:
            n = int(chunks[2])
            
    return { 'v':v, 't':t, 'n':n }
    
def parse_obj(fname):
    """Parse OBJ file.
    """
    
    vertices = []
    normals = []
    uvs = []
    
    faces = []
    
    materials = {}
    mcounter = 0
    mcurrent = 0
    
    mtllib = ""
    
    # current face state
    group = 0
    object = 0
    smooth = 0
    
    for line in fileinput.input(fname):
        chunks = line.split()
        if len(chunks) > 0:
            
            # Vertices as (x,y,z) coordinates
            # v 0.123 0.234 0.345
            if chunks[0] == "v" and len(chunks) == 4:
                x = float(chunks[1])
                y = float(chunks[2])
                z = float(chunks[3])
                vertices.append([x,y,z])

            # Normals in (x,y,z) form; normals might not be unit
            # vn 0.707 0.000 0.707
            if chunks[0] == "vn" and len(chunks) == 4:
                x = float(chunks[1])
                y = float(chunks[2])
                z = float(chunks[3])
                normals.append([x,y,z])

            # Texture coordinates in (u,v[,w]) coordinates, w is optional
            # vt 0.500 -1.352 [0.234]
            if chunks[0] == "vt" and len(chunks) >= 3:
                u = float(chunks[1])
                v = float(chunks[2])
                w = 0
                if len(chunks)>3:
                    w = float(chunks[3])
                uvs.append([u,v,w])

            # Face
            if chunks[0] == "f" and len(chunks) >= 4:
                vertex_index = []
                uv_index = []
                normal_index = []
                
                for v in chunks[1:]:
                    vertex = parse_vertex(v)
                    if vertex['v']:
                        vertex_index.append(vertex['v'])
                    if vertex['t']:
                        uv_index.append(vertex['t'])
                    if vertex['n']:
                        normal_index.append(vertex['n'])
                
                faces.append({
                    'vertex':vertex_index, 
                    'uv':uv_index,
                    'normal':normal_index,
                    
                    'material':mcurrent,
                    'group':group, 
                    'object':object, 
                    'smooth':smooth,
                    })
    
            # Group
            if chunks[0] == "g" and len(chunks) == 2:
                group = chunks[1]

            # Object
            if chunks[0] == "o" and len(chunks) == 2:
                object = chunks[1]

            # Materials definition
            if chunks[0] == "mtllib" and len(chunks) == 2:
                mtllib = chunks[1]
                
            # Material
            if chunks[0] == "usemtl" and len(chunks) == 2:
                material = chunks[1]
                if not material in materials:
                    mcurrent = mcounter
                    materials[material] = mcounter
                    mcounter += 1
                else:
                    mcurrent = materials[material]

            # Smooth shading
            if chunks[0] == "s" and len(chunks) == 2:
                smooth = chunks[1]

    return faces, vertices, uvs, normals, materials, mtllib
    
# #####################################################
# Generator
# #####################################################
def generate_vertex(v):
    return TEMPLATE_VERTEX % (v[0], v[1], v[2])
    
def generate_uv(f, uvs):
    ui = f['uv']
    if len(ui) == 3:
        return TEMPLATE_UV3 % (uvs[ui[0]-1][0], 1.0 - uvs[ui[0]-1][1],
                               uvs[ui[1]-1][0], 1.0 - uvs[ui[1]-1][1],
                               uvs[ui[2]-1][0], 1.0 - uvs[ui[2]-1][1])
    elif len(ui) == 4:
        return TEMPLATE_UV4 % (uvs[ui[0]-1][0], 1.0 - uvs[ui[0]-1][1],
                               uvs[ui[1]-1][0], 1.0 - uvs[ui[1]-1][1],
                               uvs[ui[2]-1][0], 1.0 - uvs[ui[2]-1][1],
                               uvs[ui[3]-1][0], 1.0 - uvs[ui[3]-1][1])
    return ""
    
def generate_face(f):
    vi = f['vertex']
    if f["normal"]:
        ni = f['normal']
        if len(vi) == 3:
            return TEMPLATE_FACE3N % (vi[0]-1, vi[1]-1, vi[2]-1, f['material'], ni[0]-1, ni[1]-1, ni[2]-1)
        elif len(vi) == 4:
            return TEMPLATE_FACE4N % (vi[0]-1, vi[1]-1, vi[2]-1, vi[3]-1, f['material'],  ni[0]-1, ni[1]-1, ni[2]-1, ni[3]-1)
    else:
        if len(vi) == 3:
            return TEMPLATE_FACE3 % (vi[0]-1, vi[1]-1, vi[2]-1, f['material'])
        elif len(vi) == 4:
            return TEMPLATE_FACE4 % (vi[0]-1, vi[1]-1, vi[2]-1, vi[3]-1, f['material'])
    return ""

def generate_normal(n):
    return TEMPLATE_N % (n[0], n[1], n[2])

def generate_color(i):
    """Generate hex color corresponding to integer.
    
    Colors should have well defined ordering.
    First N colors are hardcoded, then colors are random 
    (must seed random number  generator with deterministic value 
    before getting colors).
    """
    
    if i < len(COLORS):
        return "0x%x" % COLORS[i]
    else:
        return "0x%x" % (int(0xffffff * random.random()) + 0xff000000)
        
def value2string(v):
    if type(v)==str and v[0] != "0":
        return '"%s"' % v
    return str(v)
    
def generate_materials(mtl, materials):
    """Generate JS array of materials objects
    
    JS material objects are basically prettified one-to-one 
    mappings of MTL properties in JSON format.
    """
    
    mtl_array = []
    for m in mtl:
        index = materials[m]
        
        # add debug information
        #  materials should be sorted according to how
        #  they appeared in OBJ file (for the first time)
        #  this index is identifier used in face definitions
        mtl[m]['a_dbg_name'] = m
        mtl[m]['a_dbg_index'] = index
        mtl[m]['a_dbg_color'] = generate_color(index)
        
        mtl_raw = ",\n".join(['\t"%s" : %s' % (n, value2string(v)) for n,v in sorted(mtl[m].items())])
        mtl_string = "\t{\n%s\n\t}" % mtl_raw
        mtl_array.append([index, mtl_string])
        
    return ",\n\n".join([m for i,m in sorted(mtl_array)])

def generate_mtl(materials):
    """Generate dummy materials (if there is no MTL file).
    """
    
    mtl = {}
    for m in materials:
        index = materials[m]
        mtl[m] = {
            'a_dbg_name': m,
            'a_dbg_index': index,
            'a_dbg_color': generate_color(index)
        }
    return mtl
    
# #####################################################
# API
# #####################################################
def convert(infile, outfile):
    """Convert infile.obj to outfile.js
    
    Here is where everything happens. If you need to automate conversions,
    just import this file as Python module and call this method.
    """
    
    if not file_exists(infile):
        print "Couldn't find [%s]" % infile
        return
        
    faces, vertices, uvs, normals, materials, mtllib = parse_obj(infile)
    
    if ALIGN == "center":
        center(vertices)
    elif ALIGN == "bottom":
        bottom(vertices)
    elif ALIGN == "top":
        top(vertices)
    
    random.seed(42) # to get well defined color order for materials
    
    uv_string = ""
    if len(uvs)>0:
        uv_string = "\n".join([generate_uv(f, uvs) for f in faces])
            

    # default materials with debug colors for when
    # there is no specified MTL, if loading failed
    # or there were null materials
    mtl = generate_mtl(materials)
    
    if mtllib:
        # create full pathname for MTL (included from OBJ)
        path = os.path.dirname(infile)
        fname = os.path.join(path, mtllib)
        
        if file_exists(fname):
            # override default materials with real ones from MTL
            # (where they exist, otherwise keep defaults)
            mtl.update(parse_mtl(fname))
        
        else:
            print "Couldn't find [%s]" % fname
    
    text = TEMPLATE_FILE % {
    "name"      : get_name(outfile),
    "vertices"  : "\n".join([generate_vertex(v) for v in vertices]),
    "faces"     : "\n".join([generate_face(f)   for f in faces]),
    "uvs"       : uv_string,
    "normals"   : ",".join(generate_normal(n) for n in normals),
    
    "materials" : generate_materials(mtl, materials),
    
    "fname"     : infile,
    "nvertex"   : len(vertices),
    "nface"     : len(faces),
    "nmaterial" : len(materials)
    }
    
    out = open(outfile, "w")
    out.write(text)
    out.close()
    
    print "%d vertices, %d faces, %d materials" % (len(vertices), len(faces), len(materials))
        
# #############################################################################
# Helpers
# #############################################################################
def usage():
    print "Usage: %s -i filename.obj -o filename.js [-a center|top|bottom]" % os.path.basename(sys.argv[0])
        
# #####################################################
# Main
# #####################################################
if __name__ == "__main__":
    
    # get parameters from the command line
    try:
        opts, args = getopt.getopt(sys.argv[1:], "hi:o:a:", ["help", "input=", "output=", "align="])
    
    except getopt.GetoptError:
        usage()
        sys.exit(2)
        
    infile = outfile = ""
    
    for o, a in opts:
        if o in ("-h", "--help"):
            usage()
            sys.exit()
        
        elif o in ("-i", "--input"):
            infile = a

        elif o in ("-o", "--output"):
            outfile = a

        elif o in ("-a", "--align"):
            if a in ("top", "bottom", "center"):
                ALIGN = a
    
    if infile == "" or outfile == "":
        usage()
        sys.exit(2)
    
    print "Converting [%s] into [%s] ..." % (infile, outfile)
    convert(infile, outfile)