要用OpenGL写东东， 必须要完成的步骤包括：
Step1.建立一个context
Step2.建立和绑写要用的shader程序
Step3.建立shader函数的赋值关系
Step4.设定输出源，即FrameBufferObject(FBO)，如果是输出到默认的FBO,就可以不用自己去设定FBO了。如果是做离屏渲染需要自己设定FBO
import sys
from PIL import Image
from OpenGL.GL import *
from OpenGL.GLU import *
from OpenGL.GLUT import *
import numpy as np
#define shader code
vertex_code='''
uniform float scale;
attribute vec2 position;
attribute vec4 color;
varying vec4 v_color;
attribute vec2 TexCoordIn;
varying vec2 TexCoordOut;
void main()
{
gl_Position = vec4(position*scale, 0.0, 1.0);
v_color = color;
TexCoordOut = TexCoordIn;
}'''
fragment_code='''
varying vec4 v_color;
varying vec2 TexCoordOut;
uniform sampler2D Texture;
void main()
{
gl_FragColor = v_color*0.2+texture2D(Texture, TexCoordOut)*0.8;
}'''
#define vertex and color array
data = np.zeros(4, dtype = [ ("position", np.float32, 2), ("color", np.float32, 4),("textureCoord",np.float32,2)] )
data['color'] = [ (1,1,0,1), (1,1,0,1), (1,1,0,1), (1,1,0,1) ]
data['position'] = [ (-1,-1), (-1,+1), (+1,-1), (+1,+1) ]
data['textureCoord']= [ (0,0), (0,1), (1,0), (1,1) ]
#define debug function
def showTextureInGLTexture2D():
im = glGetTexImage( GL_TEXTURE_2D, 0, GL_RGBA, GL_UNSIGNED_BYTE )
image=Image.frombuffer("RGBA",(512,512),im, 'raw', 'RGBA', 0, 1)
image.show()
#define useful function
def display():
glClear(GL_COLOR_BUFFER_BIT)
glDrawArrays(GL_TRIANGLE_STRIP, 0, 4)
glutSwapBuffers()
def reshape(width,height):
glViewport(0, 0, width, height)
#step1 init the context
def init():
glutInit()
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGBA)
glutCreateWindow('Hello world!')
glutReshapeWindow(512,512)
glutReshapeFunc(reshape)
glutDisplayFunc(display)
glutKeyboardFunc(keyboard)
#step 2
def initShaderProgram():
program = glCreateProgram()
vertex = glCreateShader(GL_VERTEX_SHADER)
fragment = glCreateShader(GL_FRAGMENT_SHADER)
# Set shaders source
glShaderSource(vertex, vertex_code)
glShaderSource(fragment, fragment_code)
# Compile shaders
glCompileShader(vertex)
glCompileShader(fragment)
fragSuccess=glGetShaderiv(fragment, GL_COMPILE_STATUS)
vertSuccess=glGetShaderiv(vertex, GL_COMPILE_STATUS)
print "vertext shader compile success [%s]" %(vertSuccess,)
print "fragment shader compile success [%s]" %(fragSuccess,)
if vertSuccess==0:
print glGetShaderInfoLog(vertex)
sys.exit(0)
if fragSuccess==0:
print glGetShaderInfoLog(fragment)
sys.exit(0)
glAttachShader(program, vertex)
glAttachShader(program, fragment)
glLinkProgram(program)
linksucc=glGetProgramiv(program,GL_LINK_STATUS);
print "link program success [%s]" %(linksucc,)
glUseProgram(program)
return program
#step 3.1 optional setup texture
def getTextureFromFile(file):
#convert file to bytes
image = Image.open(file).transpose(Image.FLIP_TOP_BOTTOM)
image=image.crop((0,0,512,512))
image=image.convert("RGBA")
byteImage =np.array(list(image.getdata()), np.uint8)
#setup texture
texIndex=glGenTextures(1)
glEnable( GL_TEXTURE_2D )
glBindTexture=(GL_TEXTURE_2D,texIndex)
glPixelStorei(GL_UNPACK_ALIGNMENT,1)
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP)
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP)
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR)
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR)
#make the texture the default
glTexImage2D(GL_TEXTURE_2D,0,GL_RGBA,512,512,0,GL_RGBA,GL_UNSIGNED_BYTE,byteImage)
return texIndex
#step 3
def setupShaderProgramParameters(program):
#first init VBO, then other parameters
buffer = glGenBuffers(1) # Request a buffer slot from GPU
glBindBuffer(GL_ARRAY_BUFFER, buffer) # Make this buffer the default one
glBufferData(GL_ARRAY_BUFFER, data.nbytes, data, GL_DYNAMIC_DRAW) # Upload data
loc = glGetAttribLocation(program, "position") #get the index of the attribute in program
glEnableVertexAttribArray(loc) #allow this attribute decide by index can be use
stride = data.strides[0] #define how to read buffer
offset = ctypes.c_void_p(0) #define the offset where the data begin in buffer
glVertexAttribPointer(loc, 2, GL_FLOAT, False, stride, offset)
offset = ctypes.c_void_p(data.dtype["position"].itemsize)
loc = glGetAttribLocation(program, "color")
glEnableVertexAttribArray(loc)
glVertexAttribPointer(loc, 4, GL_FLOAT, False, stride, offset)
#setup other parameters
loc = glGetUniformLocation(program, "scale")
glUniform1f(loc, 1.0)
#following code to bind uniform texture if needed
aTexture=getTextureFromFile('temp.jpg')
glActiveTexture(GL_TEXTURE0)
glBindTexture(GL_TEXTURE_2D,aTexture)
loc=glGetUniformLocation(program,"Texture")
textureId=glGetIntegerv(GL_TEXTURE_BINDING_2D) #find out the id of the current texture bind to GL_TEXTURE_2D
glUniform1i(loc,textureId)
loc= glGetAttribLocation(program, "TexCoordIn")
glEnableVertexAttribArray(loc)
offset=ctypes.c_void_p(data.dtype["color"].itemsize+8)
glVertexAttribPointer(loc,2,GL_FLOAT,False,stride,offset)
#step 4.1 optional get the image from BufferFrame
def saveImageFromFBO():
display()
data = glReadPixels (0, 0, 512, 512, GL_RGB, GL_UNSIGNED_BYTE)
image = Image.new ("RGB", (512, 512), (0, 0, 0))
image.frombytes (data)
image = image.crop ((0,0,512, 512))
image = image.transpose(Image.FLIP_TOP_BOTTOM)
image.save ('saveImage.png')
#step 4 optional if need to OSR generate a BufferFrame
def setupSelfDefineFBO():
# Setup framebuffer
framebuffer = glGenFramebuffers (1)
glBindFramebuffer(GL_FRAMEBUFFER, framebuffer)
# Setup depthbuffer
depthbuffer = glGenRenderbuffers (1)
glBindRenderbuffer (GL_RENDERBUFFER,depthbuffer)
glRenderbufferStorage (GL_RENDERBUFFER, GL_DEPTH_COMPONENT, 512, 512)
# Create texture to render to
texture = glGenTextures (1)
glBindTexture (GL_TEXTURE_2D, texture)
glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR)
glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR)
glTexImage2D (GL_TEXTURE_2D, 0, GL_RGB, w, h, 0,GL_RGB, GL_UNSIGNED_BYTE, bits)
glFramebufferTexture2D (GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0,GL_TEXTURE_2D, texture, 0);
glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, depthbuffer);
status = glCheckFramebufferStatus (GL_FRAMEBUFFER);
if status != GL_FRAMEBUFFER_COMPLETE:
print "Error in framebuffer activation"
saveImageFromFBO()
# Cleanup
glBindRenderbuffer (GL_RENDERBUFFER, 0)
glBindFramebuffer(GL_FRAMEBUFFER, 0)
glDeleteTextures ([texture])
glDeleteFramebuffers ([framebuffer])
print 'save image from FBO success'
def keyboard( keycode, x, y ):
if (keycode == 'q'):
sys.exit()
elif (keycode == ' '):
saveImageFromFBO()
if (__name__ == '__main__'):
init()
program=initShaderProgram()
setupShaderProgramParameters(program)
glutMainLoop()