如何使用 PyOpenGL 渲染文本？
How to render text with PyOpenGL?
我正在学习现代 openGL，目前我在渲染文本方面遇到了麻烦。我正在关注 C++ 中的 tutorial，但我正在尝试在 python.
中实现
这是我的代码：
from OpenGL.GL import *
from OpenGL.GLU import *
from OpenGL.GL import shaders
import glfw
import freetype
import glm
import numpy as np
from PIL import Image
import math
import time
class CharacterSlot:
def __init__(self, texture, glyph):
self.texture = texture
self.textureSize = (glyph.bitmap.width, glyph.bitmap.rows)
if isinstance(glyph, freetype.GlyphSlot):
self.bearing = (glyph.bitmap_left, glyph.bitmap_top)
self.advance = glyph.advance.x
elif isinstance(glyph, freetype.BitmapGlyph):
self.bearing = (glyph.left, glyph.top)
self.advance = None
else:
raise RuntimeError('unknown glyph type')
def _get_rendering_buffer(xpos, ypos, w, h, zfix=0.0):
return np.asarray([
xpos, ypos - h, zfix, 0.0, 1.0,
xpos, ypos, zfix, 0.0, 0.0,
xpos + w, ypos, zfix, 1.0, 0.0,
xpos, ypos - h, zfix, 0.0, 1.0,
xpos + w, ypos, zfix, 1.0, 0.0,
xpos + w, ypos - h, zfix, 1.0, 1.0
], np.float32)
VERTEX_SHADER = """
#version 330 core
layout (location = 0) in vec4 vertex; // <vec2 pos, vec2 tex>
out vec2 TexCoords;
uniform mat4 projection;
void main()
{
gl_Position = projection * vec4(vertex.xy, 0.0, 1.0);
TexCoords = vertex.zw;
}
"""
FRAGMENT_SHADER = """
#version 330 core
in vec2 TexCoords;
out vec4 color;
uniform sampler2D text;
uniform vec3 textColor;
void main()
{
vec4 sampled = vec4(1.0, 1.0, 1.0, texture(text, TexCoords).r);
color = vec4(textColor, 1.0) * sampled;
}
"""
shaderProgram = None
Characters = dict()
VBO = None
VAO = None
def initliaze():
global VERTEXT_SHADER
global FRAGMENT_SHADER
global shaderProgram
global Characters
global VBO
global VAO
#compiling shaders
vertexshader = shaders.compileShader(VERTEX_SHADER, GL_VERTEX_SHADER)
fragmentshader = shaders.compileShader(FRAGMENT_SHADER, GL_FRAGMENT_SHADER)
#creating shaderProgram
shaderProgram = shaders.compileProgram(vertexshader, fragmentshader)
#get projection
#problem
shader_projection = glGetUniformLocation(shaderProgram, "projection")
projection = glm.ortho(0.0,640,0.0,640)
glUniformMatrix4fv(shader_projection, 1, GL_FALSE, glm.value_ptr(projection));
#disable byte-alignment restriction
glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
face = freetype.Face("Vera.ttf")
face.set_char_size( 48*64 )
#load first 128 characters of ASCII set
for i in range(0,128):
face.load_char(chr(i))
glyph = face.glyph
#generate texture
texture = glGenTextures(1)
glBindTexture(GL_TEXTURE_2D, texture)
glTexImage2D(GL_TEXTURE_2D,
0,
GL_RGB,
glyph.bitmap.width, glyph.bitmap.rows,
0,
GL_RGB,
GL_UNSIGNED_BYTE,
glyph.bitmap.buffer)
#texture options
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
#now store character for later use
Characters[chr(i)] = CharacterSlot(texture,glyph)
glBindTexture(GL_TEXTURE_2D, 0);
#configure VAO/VBO for texture quads
VAO = glGenVertexArrays(1)
glBindVertexArray(VAO)
VBO = glGenBuffers(1);
glBindBuffer(GL_ARRAY_BUFFER, VBO);
glBufferData(GL_ARRAY_BUFFER, 6 * 4, None, GL_DYNAMIC_DRAW);
glEnableVertexAttribArray(0);
glVertexAttribPointer(0, 4, GL_FLOAT, GL_FALSE, 4, 0);
glBindBuffer(GL_ARRAY_BUFFER, 0);
glBindVertexArray(0);
def render_text(window,text,x,y,scale,color):
global shaderProgram
global Characters
global VBO
global VAO
face = freetype.Face("Vera.ttf")
face.set_char_size(48*64)
glUniform3f(glGetUniformLocation(shaderProgram, "textColor"),
color[0]/255,color[1]/255,color[2]/255)
glActiveTexture(GL_TEXTURE0);
for c in text:
ch = Characters[c]
w,h = ch.textureSize
w = w*scale
h = w*scale
vertices = _get_rendering_buffer(x,y,w,h)
#render glyph texture over quad
glBindTexture(GL_TEXTURE_2D, ch.texture);
#update content of VBO memory
glBindBuffer(GL_ARRAY_BUFFER, VBO);
glBufferSubData(GL_ARRAY_BUFFER, 0, len(vertices), vertices)
glBindBuffer(GL_ARRAY_BUFFER, 0);
#render quad
glDrawArrays(GL_TRIANGLES, 0, 6);
#now advance cursors for next glyph (note that advance is number of 1/64 pixels)
x += (ch.advance+6)*scale;
glBindVertexArray(0);
glBindTexture(GL_TEXTURE_2D, 0);
glfwSwapBuffers(window);
glfwPollEvents();
def main():
glfw.init()
window = glfw.create_window(640, 640,"EXAMPLE PROGRAM",None,None)
glfw.make_context_current(window)
initliaze()
while not glfw.window_should_close(window):
glfw.poll_events()
glClearColor(0,0,0,1);
glClear(GL_COLOR_BUFFER_BIT);
render_text(window,'hello',1,1,1,(100,100,100))
glfw.terminate()
if __name__ == '__main__':
main()
到目前为止，我在两方面都遇到了麻烦，我能理解。 initliaze() 中的第一个问题，以下部分出现错误。
shader_projection = glGetUniformLocation(shaderProgram, "projection")
projection = glm.ortho(0.0,640,0.0,640)
glUniformMatrix4fv(shader_projection, 1, GL_FALSE, glm.value_ptr(projection));
我已将以上部分注释掉以忽略。第二个问题在 render_text() 函数中，以下部分出现错误。
glUniform3f(glGetUniformLocation(shaderProgram, "textColor"),
color[0]/255,color[1]/255,color[2]/255)
可能还有很多地方有问题。我不明白为什么文本渲染会如此困难。我在这里错过了什么？
您错过了 glUseProgram 安装着色器程序：
shaderProgram = shaders.compileProgram(vertexshader, fragmentshader)
glUseProgram(shaderProgram) # <---
glBufferData 的第二个参数和 glBufferSubData 的第三个参数是大小 字节 :
glBufferData(GL_ARRAY_BUFFER, 6 * 4, None, GL_DYNAMIC_DRAW)
glBufferData(GL_ARRAY_BUFFER, 6 * 4 * 4, None, GL_DYNAMIC_DRAW)
glBufferSubData(GL_ARRAY_BUFFER, 0, len(vertices), vertices)
glBufferSubData(GL_ARRAY_BUFFER, 0, vertices.nbytes, vertices)
顶点属性由二维顶点坐标（x，y）和二维纹理坐标组成。从顶点属性数据数组中删除线 zfix。此外，您必须翻转纹理坐标的第二个分量（否则文本会颠倒）
def _get_rendering_buffer(xpos, ypos, w, h, zfix=0.0):
return np.asarray([
xpos, ypos - h, 0, 0,
xpos, ypos, 0, 1,
xpos + w, ypos, 1, 1,
xpos, ypos - h, 0, 0,
xpos + w, ypos, 1, 1,
xpos + w, ypos - h, 1, 0
], np.float32)
glVertexAttribIPointer 的 跨度 参数必须指定 以字节为单位 。如果 stride 为 0，则通用顶点属性被理解为紧密包装在数组中。因此在你的情况下 stride 必须是 16 或 0:
glVertexAttribPointer(0, 4, GL_FLOAT, GL_FALSE, 4, 0)
glVertexAttribPointer(0, 4, GL_FLOAT, GL_FALSE, 0, None)
face.load_char(chr(i)) 生成带有颜色通道的图像（每个像素 1 个字节）。使用内部格式和格式 GL_RED 而不是 GL_RGB 来生成二维纹理图像：
glTexImage2D(GL_TEXTURE_2D, 0, GL_RED, glyph.bitmap.width, glyph.bitmap.rows, 0,
GL_RED, GL_UNSIGNED_BYTE, glyph.bitmap.buffer)
在绘制文本之前必须绑定顶点数组：
glBindVertexArray(VAO)
for c in text:
# [...]
glDrawArrays(GL_TRIANGLES, 0, 6)
递增x时有错字，必须使用>>运算符而不是+运算符：
x += (ch.advance+6)*scale
x += (ch.advance>>6)*scale
计算 h 时出现另一个错字：
h = w*scale
h = h*scale
您必须启用 alpha blending:
glEnable(GL_BLEND)
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA)
在 NDC（归一化设备坐标）中，左下角为 (-1, -1)，右上角为 (1, 1)。以这种方式设置正交投影，即 window 的左上角位于 (0, 0):
projection = glm.ortho(0.0,640,0.0,640)
projection = glm.ortho(0, 640, 640, 0)
文本的参考点在底部。因此，您必须设置一个大于文本高度的 x 坐标：
render_text(window,'hello',1,1,1,(100,100,100))
render_text(window,'hello', 20, 50, 1, (255, 100, 100))
查看完整示例（我使用了不同的字体）：
from OpenGL.GL import *
from OpenGL.GLU import *
from OpenGL.GL import shaders
import glfw
import freetype
import glm
import numpy as np
from PIL import Image
import math
import time
fontfile = "Vera.ttf"
#fontfile = r'C:\source\resource\fonts\gnu-freefont_freesans\freesans.ttf'
class CharacterSlot:
def __init__(self, texture, glyph):
self.texture = texture
self.textureSize = (glyph.bitmap.width, glyph.bitmap.rows)
if isinstance(glyph, freetype.GlyphSlot):
self.bearing = (glyph.bitmap_left, glyph.bitmap_top)
self.advance = glyph.advance.x
elif isinstance(glyph, freetype.BitmapGlyph):
self.bearing = (glyph.left, glyph.top)
self.advance = None
else:
raise RuntimeError('unknown glyph type')
def _get_rendering_buffer(xpos, ypos, w, h, zfix=0.0):
return np.asarray([
xpos, ypos - h, 0, 0,
xpos, ypos, 0, 1,
xpos + w, ypos, 1, 1,
xpos, ypos - h, 0, 0,
xpos + w, ypos, 1, 1,
xpos + w, ypos - h, 1, 0
], np.float32)
VERTEX_SHADER = """
#version 330 core
layout (location = 0) in vec4 vertex; // <vec2 pos, vec2 tex>
out vec2 TexCoords;
uniform mat4 projection;
void main()
{
gl_Position = projection * vec4(vertex.xy, 0.0, 1.0);
TexCoords = vertex.zw;
}
"""
FRAGMENT_SHADER = """
#version 330 core
in vec2 TexCoords;
out vec4 color;
uniform sampler2D text;
uniform vec3 textColor;
void main()
{
vec4 sampled = vec4(1.0, 1.0, 1.0, texture(text, TexCoords).r);
color = vec4(textColor, 1.0) * sampled;
}
"""
shaderProgram = None
Characters = dict()
VBO = None
VAO = None
def initliaze():
global VERTEXT_SHADER
global FRAGMENT_SHADER
global shaderProgram
global Characters
global VBO
global VAO
#compiling shaders
vertexshader = shaders.compileShader(VERTEX_SHADER, GL_VERTEX_SHADER)
fragmentshader = shaders.compileShader(FRAGMENT_SHADER, GL_FRAGMENT_SHADER)
#creating shaderProgram
shaderProgram = shaders.compileProgram(vertexshader, fragmentshader)
glUseProgram(shaderProgram)
#get projection
#problem
shader_projection = glGetUniformLocation(shaderProgram, "projection")
projection = glm.ortho(0, 640, 640, 0)
glUniformMatrix4fv(shader_projection, 1, GL_FALSE, glm.value_ptr(projection))
#disable byte-alignment restriction
glPixelStorei(GL_UNPACK_ALIGNMENT, 1)
face = freetype.Face(fontfile)
face.set_char_size( 48*64 )
#load first 128 characters of ASCII set
for i in range(0,128):
face.load_char(chr(i))
glyph = face.glyph
#generate texture
texture = glGenTextures(1)
glBindTexture(GL_TEXTURE_2D, texture)
glTexImage2D(GL_TEXTURE_2D, 0, GL_RED, glyph.bitmap.width, glyph.bitmap.rows, 0,
GL_RED, GL_UNSIGNED_BYTE, glyph.bitmap.buffer)
#texture options
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE)
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE)
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR)
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR)
#now store character for later use
Characters[chr(i)] = CharacterSlot(texture,glyph)
glBindTexture(GL_TEXTURE_2D, 0)
#configure VAO/VBO for texture quads
VAO = glGenVertexArrays(1)
glBindVertexArray(VAO)
VBO = glGenBuffers(1)
glBindBuffer(GL_ARRAY_BUFFER, VBO)
glBufferData(GL_ARRAY_BUFFER, 6 * 4 * 4, None, GL_DYNAMIC_DRAW)
glEnableVertexAttribArray(0)
glVertexAttribPointer(0, 4, GL_FLOAT, GL_FALSE, 0, None)
glBindBuffer(GL_ARRAY_BUFFER, 0)
glBindVertexArray(0)
def render_text(window,text,x,y,scale,color):
global shaderProgram
global Characters
global VBO
global VAO
face = freetype.Face(fontfile)
face.set_char_size(48*64)
glUniform3f(glGetUniformLocation(shaderProgram, "textColor"),
color[0]/255,color[1]/255,color[2]/255)
glActiveTexture(GL_TEXTURE0)
glEnable(GL_BLEND)
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA)
glBindVertexArray(VAO)
for c in text:
ch = Characters[c]
w, h = ch.textureSize
w = w*scale
h = h*scale
vertices = _get_rendering_buffer(x,y,w,h)
#render glyph texture over quad
glBindTexture(GL_TEXTURE_2D, ch.texture)
#update content of VBO memory
glBindBuffer(GL_ARRAY_BUFFER, VBO)
glBufferSubData(GL_ARRAY_BUFFER, 0, vertices.nbytes, vertices)
glBindBuffer(GL_ARRAY_BUFFER, 0)
#render quad
glDrawArrays(GL_TRIANGLES, 0, 6)
#now advance cursors for next glyph (note that advance is number of 1/64 pixels)
x += (ch.advance>>6)*scale
glBindVertexArray(0)
glBindTexture(GL_TEXTURE_2D, 0)
glfw.swap_buffers(window)
glfw.poll_events()
def main():
glfw.init()
window = glfw.create_window(640, 640,"EXAMPLE PROGRAM",None,None)
glfw.make_context_current(window)
initliaze()
while not glfw.window_should_close(window):
glfw.poll_events()
glClearColor(0,0,0,1)
glClear(GL_COLOR_BUFFER_BIT)
render_text(window,'hello', 20, 50, 1, (255, 100, 100))
glfw.terminate()
if __name__ == '__main__':
main()
我正在学习现代 openGL，目前我在渲染文本方面遇到了麻烦。我正在关注 C++ 中的 tutorial，但我正在尝试在 python.
中实现这是我的代码：
from OpenGL.GL import *
from OpenGL.GLU import *
from OpenGL.GL import shaders
import glfw
import freetype
import glm
import numpy as np
from PIL import Image
import math
import time
class CharacterSlot:
def __init__(self, texture, glyph):
self.texture = texture
self.textureSize = (glyph.bitmap.width, glyph.bitmap.rows)
if isinstance(glyph, freetype.GlyphSlot):
self.bearing = (glyph.bitmap_left, glyph.bitmap_top)
self.advance = glyph.advance.x
elif isinstance(glyph, freetype.BitmapGlyph):
self.bearing = (glyph.left, glyph.top)
self.advance = None
else:
raise RuntimeError('unknown glyph type')
def _get_rendering_buffer(xpos, ypos, w, h, zfix=0.0):
return np.asarray([
xpos, ypos - h, zfix, 0.0, 1.0,
xpos, ypos, zfix, 0.0, 0.0,
xpos + w, ypos, zfix, 1.0, 0.0,
xpos, ypos - h, zfix, 0.0, 1.0,
xpos + w, ypos, zfix, 1.0, 0.0,
xpos + w, ypos - h, zfix, 1.0, 1.0
], np.float32)
VERTEX_SHADER = """
#version 330 core
layout (location = 0) in vec4 vertex; // <vec2 pos, vec2 tex>
out vec2 TexCoords;
uniform mat4 projection;
void main()
{
gl_Position = projection * vec4(vertex.xy, 0.0, 1.0);
TexCoords = vertex.zw;
}
"""
FRAGMENT_SHADER = """
#version 330 core
in vec2 TexCoords;
out vec4 color;
uniform sampler2D text;
uniform vec3 textColor;
void main()
{
vec4 sampled = vec4(1.0, 1.0, 1.0, texture(text, TexCoords).r);
color = vec4(textColor, 1.0) * sampled;
}
"""
shaderProgram = None
Characters = dict()
VBO = None
VAO = None
def initliaze():
global VERTEXT_SHADER
global FRAGMENT_SHADER
global shaderProgram
global Characters
global VBO
global VAO
#compiling shaders
vertexshader = shaders.compileShader(VERTEX_SHADER, GL_VERTEX_SHADER)
fragmentshader = shaders.compileShader(FRAGMENT_SHADER, GL_FRAGMENT_SHADER)
#creating shaderProgram
shaderProgram = shaders.compileProgram(vertexshader, fragmentshader)
#get projection
#problem
shader_projection = glGetUniformLocation(shaderProgram, "projection")
projection = glm.ortho(0.0,640,0.0,640)
glUniformMatrix4fv(shader_projection, 1, GL_FALSE, glm.value_ptr(projection));
#disable byte-alignment restriction
glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
face = freetype.Face("Vera.ttf")
face.set_char_size( 48*64 )
#load first 128 characters of ASCII set
for i in range(0,128):
face.load_char(chr(i))
glyph = face.glyph
#generate texture
texture = glGenTextures(1)
glBindTexture(GL_TEXTURE_2D, texture)
glTexImage2D(GL_TEXTURE_2D,
0,
GL_RGB,
glyph.bitmap.width, glyph.bitmap.rows,
0,
GL_RGB,
GL_UNSIGNED_BYTE,
glyph.bitmap.buffer)
#texture options
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
#now store character for later use
Characters[chr(i)] = CharacterSlot(texture,glyph)
glBindTexture(GL_TEXTURE_2D, 0);
#configure VAO/VBO for texture quads
VAO = glGenVertexArrays(1)
glBindVertexArray(VAO)
VBO = glGenBuffers(1);
glBindBuffer(GL_ARRAY_BUFFER, VBO);
glBufferData(GL_ARRAY_BUFFER, 6 * 4, None, GL_DYNAMIC_DRAW);
glEnableVertexAttribArray(0);
glVertexAttribPointer(0, 4, GL_FLOAT, GL_FALSE, 4, 0);
glBindBuffer(GL_ARRAY_BUFFER, 0);
glBindVertexArray(0);
def render_text(window,text,x,y,scale,color):
global shaderProgram
global Characters
global VBO
global VAO
face = freetype.Face("Vera.ttf")
face.set_char_size(48*64)
glUniform3f(glGetUniformLocation(shaderProgram, "textColor"),
color[0]/255,color[1]/255,color[2]/255)
glActiveTexture(GL_TEXTURE0);
for c in text:
ch = Characters[c]
w,h = ch.textureSize
w = w*scale
h = w*scale
vertices = _get_rendering_buffer(x,y,w,h)
#render glyph texture over quad
glBindTexture(GL_TEXTURE_2D, ch.texture);
#update content of VBO memory
glBindBuffer(GL_ARRAY_BUFFER, VBO);
glBufferSubData(GL_ARRAY_BUFFER, 0, len(vertices), vertices)
glBindBuffer(GL_ARRAY_BUFFER, 0);
#render quad
glDrawArrays(GL_TRIANGLES, 0, 6);
#now advance cursors for next glyph (note that advance is number of 1/64 pixels)
x += (ch.advance+6)*scale;
glBindVertexArray(0);
glBindTexture(GL_TEXTURE_2D, 0);
glfwSwapBuffers(window);
glfwPollEvents();
def main():
glfw.init()
window = glfw.create_window(640, 640,"EXAMPLE PROGRAM",None,None)
glfw.make_context_current(window)
initliaze()
while not glfw.window_should_close(window):
glfw.poll_events()
glClearColor(0,0,0,1);
glClear(GL_COLOR_BUFFER_BIT);
render_text(window,'hello',1,1,1,(100,100,100))
glfw.terminate()
if __name__ == '__main__':
main()
到目前为止，我在两方面都遇到了麻烦，我能理解。 initliaze() 中的第一个问题，以下部分出现错误。
shader_projection = glGetUniformLocation(shaderProgram, "projection")
projection = glm.ortho(0.0,640,0.0,640)
glUniformMatrix4fv(shader_projection, 1, GL_FALSE, glm.value_ptr(projection));
我已将以上部分注释掉以忽略。第二个问题在 render_text() 函数中，以下部分出现错误。
glUniform3f(glGetUniformLocation(shaderProgram, "textColor"),
color[0]/255,color[1]/255,color[2]/255)
可能还有很多地方有问题。我不明白为什么文本渲染会如此困难。我在这里错过了什么？
您错过了 glUseProgram 安装着色器程序：
shaderProgram = shaders.compileProgram(vertexshader, fragmentshader)
glUseProgram(shaderProgram) # <---
glBufferData 的第二个参数和 glBufferSubData 的第三个参数是大小 字节 :
glBufferData(GL_ARRAY_BUFFER, 6 * 4, None, GL_DYNAMIC_DRAW)
glBufferData(GL_ARRAY_BUFFER, 6 * 4 * 4, None, GL_DYNAMIC_DRAW)
glBufferSubData(GL_ARRAY_BUFFER, 0, len(vertices), vertices)
glBufferSubData(GL_ARRAY_BUFFER, 0, vertices.nbytes, vertices)
顶点属性由二维顶点坐标（x，y）和二维纹理坐标组成。从顶点属性数据数组中删除线 zfix。此外，您必须翻转纹理坐标的第二个分量（否则文本会颠倒）
def _get_rendering_buffer(xpos, ypos, w, h, zfix=0.0):
return np.asarray([
xpos, ypos - h, 0, 0,
xpos, ypos, 0, 1,
xpos + w, ypos, 1, 1,
xpos, ypos - h, 0, 0,
xpos + w, ypos, 1, 1,
xpos + w, ypos - h, 1, 0
], np.float32)
glVertexAttribIPointer 的 跨度 参数必须指定 以字节为单位 。如果 stride 为 0，则通用顶点属性被理解为紧密包装在数组中。因此在你的情况下 stride 必须是 16 或 0:
glVertexAttribPointer(0, 4, GL_FLOAT, GL_FALSE, 4, 0)
glVertexAttribPointer(0, 4, GL_FLOAT, GL_FALSE, 0, None)
face.load_char(chr(i)) 生成带有颜色通道的图像（每个像素 1 个字节）。使用内部格式和格式 GL_RED 而不是 GL_RGB 来生成二维纹理图像：
glTexImage2D(GL_TEXTURE_2D, 0, GL_RED, glyph.bitmap.width, glyph.bitmap.rows, 0,
GL_RED, GL_UNSIGNED_BYTE, glyph.bitmap.buffer)
在绘制文本之前必须绑定顶点数组：
glBindVertexArray(VAO)
for c in text:
# [...]
glDrawArrays(GL_TRIANGLES, 0, 6)
递增x时有错字，必须使用>>运算符而不是+运算符：
x += (ch.advance+6)*scale
x += (ch.advance>>6)*scale
计算 h 时出现另一个错字：
h = w*scale
h = h*scale
您必须启用 alpha blending:
glEnable(GL_BLEND)
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA)
在 NDC（归一化设备坐标）中，左下角为 (-1, -1)，右上角为 (1, 1)。以这种方式设置正交投影，即 window 的左上角位于 (0, 0):
projection = glm.ortho(0.0,640,0.0,640)
projection = glm.ortho(0, 640, 640, 0)
文本的参考点在底部。因此，您必须设置一个大于文本高度的 x 坐标：
render_text(window,'hello',1,1,1,(100,100,100))
render_text(window,'hello', 20, 50, 1, (255, 100, 100))
查看完整示例（我使用了不同的字体）：
from OpenGL.GL import *
from OpenGL.GLU import *
from OpenGL.GL import shaders
import glfw
import freetype
import glm
import numpy as np
from PIL import Image
import math
import time
fontfile = "Vera.ttf"
#fontfile = r'C:\source\resource\fonts\gnu-freefont_freesans\freesans.ttf'
class CharacterSlot:
def __init__(self, texture, glyph):
self.texture = texture
self.textureSize = (glyph.bitmap.width, glyph.bitmap.rows)
if isinstance(glyph, freetype.GlyphSlot):
self.bearing = (glyph.bitmap_left, glyph.bitmap_top)
self.advance = glyph.advance.x
elif isinstance(glyph, freetype.BitmapGlyph):
self.bearing = (glyph.left, glyph.top)
self.advance = None
else:
raise RuntimeError('unknown glyph type')
def _get_rendering_buffer(xpos, ypos, w, h, zfix=0.0):
return np.asarray([
xpos, ypos - h, 0, 0,
xpos, ypos, 0, 1,
xpos + w, ypos, 1, 1,
xpos, ypos - h, 0, 0,
xpos + w, ypos, 1, 1,
xpos + w, ypos - h, 1, 0
], np.float32)
VERTEX_SHADER = """
#version 330 core
layout (location = 0) in vec4 vertex; // <vec2 pos, vec2 tex>
out vec2 TexCoords;
uniform mat4 projection;
void main()
{
gl_Position = projection * vec4(vertex.xy, 0.0, 1.0);
TexCoords = vertex.zw;
}
"""
FRAGMENT_SHADER = """
#version 330 core
in vec2 TexCoords;
out vec4 color;
uniform sampler2D text;
uniform vec3 textColor;
void main()
{
vec4 sampled = vec4(1.0, 1.0, 1.0, texture(text, TexCoords).r);
color = vec4(textColor, 1.0) * sampled;
}
"""
shaderProgram = None
Characters = dict()
VBO = None
VAO = None
def initliaze():
global VERTEXT_SHADER
global FRAGMENT_SHADER
global shaderProgram
global Characters
global VBO
global VAO
#compiling shaders
vertexshader = shaders.compileShader(VERTEX_SHADER, GL_VERTEX_SHADER)
fragmentshader = shaders.compileShader(FRAGMENT_SHADER, GL_FRAGMENT_SHADER)
#creating shaderProgram
shaderProgram = shaders.compileProgram(vertexshader, fragmentshader)
glUseProgram(shaderProgram)
#get projection
#problem
shader_projection = glGetUniformLocation(shaderProgram, "projection")
projection = glm.ortho(0, 640, 640, 0)
glUniformMatrix4fv(shader_projection, 1, GL_FALSE, glm.value_ptr(projection))
#disable byte-alignment restriction
glPixelStorei(GL_UNPACK_ALIGNMENT, 1)
face = freetype.Face(fontfile)
face.set_char_size( 48*64 )
#load first 128 characters of ASCII set
for i in range(0,128):
face.load_char(chr(i))
glyph = face.glyph
#generate texture
texture = glGenTextures(1)
glBindTexture(GL_TEXTURE_2D, texture)
glTexImage2D(GL_TEXTURE_2D, 0, GL_RED, glyph.bitmap.width, glyph.bitmap.rows, 0,
GL_RED, GL_UNSIGNED_BYTE, glyph.bitmap.buffer)
#texture options
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE)
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE)
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR)
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR)
#now store character for later use
Characters[chr(i)] = CharacterSlot(texture,glyph)
glBindTexture(GL_TEXTURE_2D, 0)
#configure VAO/VBO for texture quads
VAO = glGenVertexArrays(1)
glBindVertexArray(VAO)
VBO = glGenBuffers(1)
glBindBuffer(GL_ARRAY_BUFFER, VBO)
glBufferData(GL_ARRAY_BUFFER, 6 * 4 * 4, None, GL_DYNAMIC_DRAW)
glEnableVertexAttribArray(0)
glVertexAttribPointer(0, 4, GL_FLOAT, GL_FALSE, 0, None)
glBindBuffer(GL_ARRAY_BUFFER, 0)
glBindVertexArray(0)
def render_text(window,text,x,y,scale,color):
global shaderProgram
global Characters
global VBO
global VAO
face = freetype.Face(fontfile)
face.set_char_size(48*64)
glUniform3f(glGetUniformLocation(shaderProgram, "textColor"),
color[0]/255,color[1]/255,color[2]/255)
glActiveTexture(GL_TEXTURE0)
glEnable(GL_BLEND)
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA)
glBindVertexArray(VAO)
for c in text:
ch = Characters[c]
w, h = ch.textureSize
w = w*scale
h = h*scale
vertices = _get_rendering_buffer(x,y,w,h)
#render glyph texture over quad
glBindTexture(GL_TEXTURE_2D, ch.texture)
#update content of VBO memory
glBindBuffer(GL_ARRAY_BUFFER, VBO)
glBufferSubData(GL_ARRAY_BUFFER, 0, vertices.nbytes, vertices)
glBindBuffer(GL_ARRAY_BUFFER, 0)
#render quad
glDrawArrays(GL_TRIANGLES, 0, 6)
#now advance cursors for next glyph (note that advance is number of 1/64 pixels)
x += (ch.advance>>6)*scale
glBindVertexArray(0)
glBindTexture(GL_TEXTURE_2D, 0)
glfw.swap_buffers(window)
glfw.poll_events()
def main():
glfw.init()
window = glfw.create_window(640, 640,"EXAMPLE PROGRAM",None,None)
glfw.make_context_current(window)
initliaze()
while not glfw.window_should_close(window):
glfw.poll_events()
glClearColor(0,0,0,1)
glClear(GL_COLOR_BUFFER_BIT)
render_text(window,'hello', 20, 50, 1, (255, 100, 100))
glfw.terminate()
if __name__ == '__main__':
main()