source: trunk/glFreeType.py @ 978

#       A quick and simple opengl font library that uses GNU freetype2, written
#       and distributed as part of a tutorial for nehe.gamedev.net.
#       Sven Olsen, 2003
#       Translated to PyOpenGL by Brian Leair, 2004
# 
#

# We are going to use Python Image Library's font handling
# From PIL 1.1.4:
import ImageFont
from OpenGL.GL import *
from OpenGL.GLU import *

def is_font_available (ft, facename):
        """ Returns true if FreeType can find the requested face name 
                Pass the basname of the font e.g. "arial" or "times new roman"
        """
        if (facename in ft.available_fonts ()):
                return True
        return False

def next_p2 (num):
        """ If num isn't a power of 2, will return the next higher power of two """
        rval = 1
        while (rval<num):
                rval <<= 1
        return rval

def make_dlist (ft, ch, list_base, tex_base_list):
        """ Given an integer char code, build a GL texture into texture_array,
                build a GL display list for display list number display_list_base + ch.
                Populate the glTexture for the integer ch and construct a display
                list that renders the texture for ch.
                Note, that display_list_base and texture_base are supposed
                to be preallocated for 128 consecutive display lists and and 
                array of textures.
        """

        # //The first thing we do is get FreeType to render our character
        # //into a bitmap.  This actually requires a couple of FreeType commands:
        # //Load the Glyph for our character.
        # //Move the face's glyph into a Glyph object.
        # //Convert the glyph to a bitmap.
        # //This reference will make accessing the bitmap easier
        # - This is the 2 dimensional Numeric array

        # Use our helper function to get the widths of
        # the bitmap data that we will need in order to create
        # our texture.
        glyph = ft.getmask (chr (ch))
        glyph_width, glyph_height = glyph.size 
        # We are using PIL's wrapping for FreeType. As a result, we don't have 
        # direct access to glyph.advance or other attributes, so we add a 1 pixel pad.
        width = next_p2 (glyph_width + 1)
        height = next_p2 (glyph_height + 1)


        # python GL will accept lists of integers or strings, but not Numeric arrays
        # so, we buildup a string for our glyph's texture from the Numeric bitmap 

        # Here we fill in the data for the expanded bitmap.
        # Notice that we are using two channel bitmap (one for
        # luminocity and one for alpha), but we assign
        # both luminocity and alpha to the value that we
        # find in the FreeType bitmap. 
        # We use the ?: operator so that value which we use
        # will be 0 if we are in the padding zone, and whatever
        # is the the Freetype bitmap otherwise.
        expanded_data = ""
        for j in xrange (height):
                for i in xrange (width):
                        if (i >= glyph_width) or (j >= glyph_height):
                                value = chr (0)
                                expanded_data += value
                                expanded_data += value
                        else:
                                value = chr (glyph.getpixel ((i, j)))
                                expanded_data += value
                                expanded_data += value

        # -------------- Build the gl texture ------------

        # Now we just setup some texture paramaters.
        ID = glGenTextures (1)
        tex_base_list [ch] = ID
        glBindTexture (GL_TEXTURE_2D, ID)
        glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR)
        glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR)

        border = 0
        # Here we actually create the texture itself, notice
        # that we are using GL_LUMINANCE_ALPHA to indicate that
        # we are using 2 channel data.
        glTexImage2D( GL_TEXTURE_2D, 0, GL_RGBA, width, height,
                border, GL_LUMINANCE_ALPHA, GL_UNSIGNED_BYTE, expanded_data )

        # With the texture created, we don't need to expanded data anymore
        expanded_data = None

        # --- Build the gl display list that draws the texture for this character ---

        # So now we can create the display list
        glNewList (list_base + ch, GL_COMPILE)

        if (ch == ord (" ")):
                glyph_advance = glyph_width
                glTranslatef(glyph_advance, 0, 0)
                glEndList()
        else:

                glBindTexture (GL_TEXTURE_2D, ID)

                glPushMatrix()

                # // first we need to move over a little so that
                # // the character has the right amount of space
                # // between it and the one before it.
                # glyph_left = glyph.bbox [0]
                # glTranslatef(glyph_left, 0, 0)

                # // Now we move down a little in the case that the
                # // bitmap extends past the bottom of the line 
                # // this is only true for characters like 'g' or 'y'.
                # glyph_descent = glyph.decent
                # glTranslatef(0, glyph_descent, 0)

                # //Now we need to account for the fact that many of
                # //our textures are filled with empty padding space.
                # //We figure what portion of the texture is used by 
                # //the actual character and store that information in 
                # //the x and y variables, then when we draw the
                # //quad, we will only reference the parts of the texture
                # //that we contain the character itself.
                x=float (glyph_width) / float (width)
                y=float (glyph_height) / float (height)

                # //Here we draw the texturemaped quads.
                # //The bitmap that we got from FreeType was not 
                # //oriented quite like we would like it to be,
                # //so we need to link the texture to the quad
                # //so that the result will be properly aligned.
                glBegin(GL_QUADS)
                glTexCoord2f(0,0), glVertex2f(0,glyph_height)
                glTexCoord2f(0,y), glVertex2f(0,0)
                glTexCoord2f(x,y), glVertex2f(glyph_width,0)
                glTexCoord2f(x,0), glVertex2f(glyph_width, glyph_height)
                glEnd()
                glPopMatrix()

                # Note, PIL's FreeType interface hides the advance from us.
                # Normal PIL clients are rendering an entire string through FreeType, not
                # a single character at a time like we are doing here.
                # Because the advance value is hidden from we will advance
                # the "pen" based upon the rendered glyph's width. This is imperfect.
                glTranslatef(glyph_width + 0.75, 0, 0)

                # //increment the raster position as if we were a bitmap font.
                # //(only needed if you want to calculate text length)
                # //glBitmap(0,0,0,0,face->glyph->advance.x >> 6,0,NULL)

                # //Finnish the display list
                glEndList()

        return

# /// A fairly straight forward function that pushes
# /// a projection matrix that will make object world 
# /// coordinates identical to window coordinates.
def pushScreenCoordinateMatrix():
        glPushAttrib(GL_TRANSFORM_BIT)
        viewport = glGetIntegerv(GL_VIEWPORT)
        glMatrixMode(GL_PROJECTION)
        glPushMatrix()
        glLoadIdentity()
        gluOrtho2D(viewport[0],viewport[2],viewport[1],viewport[3])
        glPopAttrib()
        return


# Pops the projection matrix without changing the current
# MatrixMode.
def pop_projection_matrix():
        glPushAttrib(GL_TRANSFORM_BIT)
        glMatrixMode(GL_PROJECTION)
        glPopMatrix()
        glPopAttrib()
        return


class font_data:
        def __init__ (self, facename, pixel_height):
                # We haven't yet allocated textures or display lists
                self.m_allocated = False
                self.m_font_height = pixel_height
                self.m_facename = facename

                # Try to obtain the FreeType font
                try:
                        ft = ImageFont.truetype (facename, pixel_height)
           #ft = ImageFont.load ("D:\python27-64\Lib\site-packages\PIL\Images\courB08.pil")
                except:
                        raise ValueError, "Unable to locate font '%s'" % (facename)

                # Here we ask opengl to allocate resources for
                # all the textures and displays lists which we
                # are about to create.  
                self.m_list_base = glGenLists (128)

                # Consturct a list of 128 elements. This
                # list will be assigned the texture IDs we create for each glyph
                self.textures = [None] * 128

                # This is where we actually create each of the fonts display lists.
                for i in range (1,128):
                        make_dlist (ft, i, self.m_list_base, self.textures);

                self.m_allocated = True


                # //We don't need the face information now that the display
                # //lists have been created, so we free the assosiated resources.
                # Note: Don't need this, as python will decref and dealloc the ft for us.
                ft = None
                return

        def glPrint (self, x, y, string):
                """
                # ///Much like Nehe's glPrint function, but modified to work
                # ///with freetype fonts.
                """
                # We want a coordinate system where things coresponding to window pixels.
                pushScreenCoordinateMatrix()
        
                # //We make the height about 1.5* that of
                h = float (self.m_font_height) / 0.63           
        
                # If There's No Text
                # Do Nothing
                if (string == None):
                        pop_projection_matrix()
                        return
                if (string == ""):
                        pop_projection_matrix()
                        return

                # //Here is some code to split the text that we have been
                # //given into a set of lines.  
                # //This could be made much neater by using
                # //a regular expression library such as the one avliable from
                # //boost.org (I've only done it out by hand to avoid complicating
                # //this tutorial with unnecessary library dependencies).
                # //Note: python string object has convenience method for this :)
                lines = string.split ("\n")

                glPushAttrib(GL_LIST_BIT | GL_CURRENT_BIT  | GL_ENABLE_BIT | GL_TRANSFORM_BIT)
                glMatrixMode(GL_MODELVIEW)
                glDisable(GL_LIGHTING)
                glEnable(GL_TEXTURE_2D)
                glDisable(GL_DEPTH_TEST)
                glEnable(GL_BLEND)
                glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA)

                glListBase(self.m_list_base)
                modelview_matrix = glGetFloatv(GL_MODELVIEW_MATRIX)

                # //This is where the text display actually happens.
                # //For each line of text we reset the modelview matrix
                # //so that the line's text will start in the correct position.
                # //Notice that we need to reset the matrix, rather than just translating
                # //down by h. This is because when each character is
                # //draw it modifies the current matrix so that the next character
                # //will be drawn immediatly after it.  
                for i in xrange (len (lines)):
                        line = lines [i]

                        glPushMatrix ()
                        glLoadIdentity ()
                        glTranslatef (x,y-h*i,0);
                        glMultMatrixf (modelview_matrix);

                        # //  The commented out raster position stuff can be useful if you need to
                        # //  know the length of the text that you are creating.
                        # //  If you decide to use it make sure to also uncomment the glBitmap command
                        # //  in make_dlist().
                        # //    glRasterPos2f(0,0);
                        glCallLists (line)
                        # //    rpos = glGetFloatv (GL_CURRENT_RASTER_POSITION)
                        # //    float len=x-rpos[0];
                        glPopMatrix()

                glPopAttrib()
                pop_projection_matrix()
                return

        def release (self):
                """ Release the gl resources for this Face.
                        (This provides the functionality of KillFont () and font_data::clean ()
                """
                if (self.m_allocated):
                        # Free up the glTextures and the display lists for our face
                        glDeleteLists ( self.m_list_base, 128);
                        for ID in self.textures:
                                glDeleteTextures (ID);
                        # Extra defensive. Clients that continue to try and use this object
                        # will now trigger exceptions.
                        self.list_base = None
                        self.m_allocated = False
                return

        def __del__ (self):
                """ Python destructor for when no more refs to this Face object """
                self.release ()
                return


# Unit Test harness if this python module is run directly.
if __name__ == "__main__":
        print "testing availability of freetype font courier\n"
        ft = ImageFont.load ("D:\python27-64\Lib\site-packages\PIL\Images\courB08.pil")
        if ft:
                print "Found the font"
        else:
                print "failed to find the font\n"