python - 在 OpenGL 窗口中可视化单个字符(python)
问题描述
使用以下代码,我想在 opengl 窗口中显示单个字符,但是如果字符以较小的尺寸在水平和垂直方向上多次打印到一个空间中,我认为与字符应该一样大,我得到的只是. 谢谢你。
代码(几乎全部):
import numpy
from freetype import *
import OpenGL.GL as gl
import OpenGL.GLUT as glut
text = 'H'
def makefont(filename, size):
face = Face(filename)
face.set_char_size( size*64 )
face.load_char(text, FT_LOAD_RENDER | FT_LOAD_FORCE_AUTOHINT)
bitmap = face.glyph.bitmap
data = bitmap.buffer
rows = bitmap.rows
width = bitmap.width
ascender = face.glyph.bitmap_top
descender = bitmap.rows-face.glyph.bitmap_top
height = ascender+descender
imageData = numpy.array(bitmap.buffer, numpy.uint8).reshape(rows,width)
imageData = imageData[::-1,:]
#########
textureID = gl.glGenTextures(1)
gl.glBindTexture( gl.GL_TEXTURE_2D, textureID )
gl.glTexParameterf( gl.GL_TEXTURE_2D, gl.GL_TEXTURE_MAG_FILTER, gl.GL_LINEAR )
gl.glTexParameterf( gl.GL_TEXTURE_2D, gl.GL_TEXTURE_MIN_FILTER, gl.GL_LINEAR )
gl.glTexImage2D( gl.GL_TEXTURE_2D, 0, gl.GL_RGBA, width, height, 0,
gl.GL_RGBA, gl.GL_UNSIGNED_BYTE, imageData )
#
gl.glBindTexture(gl.GL_TEXTURE_2D, textureID)
gl.glBegin(gl.GL_QUADS)
gl.glTexCoord2f(0, 0)
x = 0
y = 0
w = width
h = height
gl.glVertex2f(x, y)
gl.glTexCoord2f(1, 0)
gl.glVertex2f(x + w, y)
gl.glTexCoord2f(1, 1)
gl.glVertex2f(x + w, y + h)
gl.glTexCoord2f(0, 1)
gl.glVertex2f( x, y + h)
gl.glEnd()
def on_display( ):
gl.glClearColor(1,1,1,1)
gl.glClear(gl.GL_COLOR_BUFFER_BIT | gl.GL_DEPTH_BUFFER_BIT)
gl.glColor(0,0,0,1)
makefont( './VeraMono.ttf', 64 )
glut.glutSwapBuffers( )
def on_reshape( width, height ):
#
if __name__ == '__main__':
import sys
glut.glutInitDisplayMode( glut.GLUT_DOUBLE | glut.GLUT_RGB | glut.GLUT_DEPTH )
gl.glTexEnvf( gl.GL_TEXTURE_ENV, gl.GL_TEXTURE_ENV_MODE, gl.GL_MODULATE )
gl.glEnable( gl.GL_DEPTH_TEST )
gl.glEnable( gl.GL_BLEND )
gl.glEnable( gl.GL_COLOR_MATERIAL )
gl.glColorMaterial( gl.GL_FRONT_AND_BACK, gl.GL_AMBIENT_AND_DIFFUSE )
gl.glBlendFunc( gl.GL_SRC_ALPHA, gl.GL_ONE_MINUS_SRC_ALPHA )
gl.glEnable( gl.GL_TEXTURE_2D )
glut.glutMainLoop( )
解决方案
由 freetype 库渲染的字形图像只有 1 个颜色通道。用于GL_ALPHA
纹理的格式和内部格式。见glTexImage2D
。
此外,您还必须更改GL_UNPACK_ALIGNMENT
参数。GL_UNPACK_ALIGNMENT
当从缓冲区读取图像时,该参数定义图像每行(行)中第一个像素的对齐方式。默认情况下,此参数为 4。
字形图像的每个像素都以一个字节编码,并且图像被紧密打包。因此字形图像的对齐方式为 1,并且必须在读取图像和指定纹理之前更改参数:
gl.glPixelStorei(gl.GL_UNPACK_ALIGNMENT, 1)
gl.glTexImage2D(gl.GL_TEXTURE_2D, 0, gl.GL_ALPHA, width, height, 0,
gl.GL_ALPHA, gl.GL_UNSIGNED_BYTE, imageData)
由于您没有设置任何投影矩阵,因此您必须在标准化设备空间中绘制几何图形。在标准化设备空间中,所有坐标都处于范围 [-1.0, 1.0] 中:
x, y, w, h = -1, -1, 2, 2
gl.glBegin(gl.GL_QUADS)
gl.glTexCoord2f(0, 0)
gl.glVertex2f(x, y)
gl.glTexCoord2f(1, 0)
gl.glVertex2f(x + w, y)
gl.glTexCoord2f(1, 1)
gl.glVertex2f(x + w, y + h)
gl.glTexCoord2f(0, 1)
gl.glVertex2f( x, y + h)
gl.glEnd()
如果要使用窗口坐标,则必须通过以下方式设置正交投影glOrtho
:
gl.glMatrixMode(gl.GL_PROJECTION)
gl.glLoadIdentity()
gl.glOrtho(0, width, height, 0, -1, 1)
gl.glMatrixMode(gl.GL_MODELVIEW)
x, y, w, h = 0, 0, width, height
gl.glBegin(gl.GL_QUADS)
gl.glTexCoord2f(0, 0)
gl.glVertex2f(x, y)
gl.glTexCoord2f(1, 0)
gl.glVertex2f(x + w, y)
gl.glTexCoord2f(1, 1)
gl.glVertex2f(x + w, y + h)
gl.glTexCoord2f(0, 1)
gl.glVertex2f( x, y + h)
gl.glEnd()
完整的功能makefont
和on_reshape
:
def makefont(filename, size):
face = Face(filename)
face.set_char_size( size*64 )
face.load_char(text, FT_LOAD_RENDER | FT_LOAD_FORCE_AUTOHINT)
bitmap = face.glyph.bitmap
data = bitmap.buffer
rows = bitmap.rows
width = bitmap.width
ascender = face.glyph.bitmap_top
descender = bitmap.rows-face.glyph.bitmap_top
height = ascender+descender
imageData = numpy.array(bitmap.buffer, numpy.uint8).reshape(rows,width)
imageData = imageData[::-1,:]
textureID = gl.glGenTextures(1)
gl.glBindTexture( gl.GL_TEXTURE_2D, textureID )
gl.glTexParameterf( gl.GL_TEXTURE_2D, gl.GL_TEXTURE_MAG_FILTER, gl.GL_LINEAR )
gl.glTexParameterf( gl.GL_TEXTURE_2D, gl.GL_TEXTURE_MIN_FILTER, gl.GL_LINEAR )
gl.glPixelStorei(gl.GL_UNPACK_ALIGNMENT, 1)
gl.glTexImage2D(gl.GL_TEXTURE_2D, 0, gl.GL_ALPHA, width, height, 0,
gl.GL_ALPHA, gl.GL_UNSIGNED_BYTE, imageData)
x, y, w, h = 0, 0, width, height
gl.glBindTexture(gl.GL_TEXTURE_2D, textureID)
gl.glBegin(gl.GL_QUADS)
gl.glTexCoord2f(0, 0)
gl.glVertex2f(x, y)
gl.glTexCoord2f(1, 0)
gl.glVertex2f(x + w, y)
gl.glTexCoord2f(1, 1)
gl.glVertex2f(x + w, y + h)
gl.glTexCoord2f(0, 1)
gl.glVertex2f( x, y + h)
gl.glEnd()
def on_reshape( width, height ):
gl.glViewport(0, 0, width, height)
gl.glMatrixMode(gl.GL_PROJECTION)
gl.glLoadIdentity()
gl.glOrtho(0, width, height, 0, -1, 1)
gl.glMatrixMode(gl.GL_MODELVIEW)
另请参阅立即模式和旧版 OpenGL
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