YaronGh YaronGh - 4 months ago 34
Python Question

OpenGL (python) - display an image?

I'm trying to use PyQT and the Python binding for OpenGL to display an image on a rectangle. So far, here's my code:

gVShader = """
attribute vec4 position;
attribute vec2 texture_coordinates;
varying vec4 dstColor;
varying vec2 v_texture_coordinates;

void main() {
v_texture_coordinates = texture_coordinates;
gl_Position = position;
}"""

gFShader = """
uniform sampler2D texture1;
varying vec2 v_texture_coordinates;

void main() {

gl_FragColor = texture2D(texture1, v_texture_coordinates);
}"""
class ProjectiveGLViewer(QtOpenGL.QGLWidget):

def __init__(self, parent=None):
super(ProjectiveGLViewer, self).__init__(parent)


def initializeGL(self):

# load the shaders source code

vshader = QtOpenGL.QGLShader(QtOpenGL.QGLShader.Vertex, self)
if not vshader.compileSourceCode(gVShader):
print vshader.log()

fshader = QtOpenGL.QGLShader(QtOpenGL.QGLShader.Fragment, self)
if not fshader.compileSourceCode(gFShader):
print fshader.log()

# create the shader program, compile, attach shaders to the program, link and use the program

self._program = QtOpenGL.QGLShaderProgram()
self._program.addShader(vshader)
self._program.addShader(fshader)
self._program.link()
self._program.bind()

# data array (2 [position], 2 [texture coordinates])

data = np.array([-1.0, -1.0, 0.0, 0.0, 1.0, -1.0, 1.0, 0.0, -1.0, 1.0, 0.0, 1.0, 1.0, 1.0, 1.0, 1.0], dtype=np.float32)

# create a buffer and bind it to the 'data' array

self.bufferID = glGenBuffers(1)
glBindBuffer(GL_ARRAY_BUFFER, self.bufferID)
glBufferData(GL_ARRAY_BUFFER, data.nbytes, data, GL_DYNAMIC_DRAW)

# tell OpenGL how to handle the buffer of data that is already on the GPU

loc = self._program.attributeLocation("position")
glEnableVertexAttribArray(loc)
glVertexAttribPointer(loc, 2, GL_FLOAT, False, 16, ctypes.c_void_p(0))

loc = self._program.attributeLocation("texture_coordinates")
glEnableVertexAttribArray(loc)
glVertexAttribPointer(loc, 2, GL_FLOAT, False, 16, ctypes.c_void_p(8))

self._imageTextureID = glGenTextures(1)

image = QtGui.QImage("image.jpg")
ptr = image.bits()
ptr.setsize(image.byteCount())
image_data = np.asarray(ptr).reshape(image.width(), image.height(), 4)

glBindTexture(GL_TEXTURE_2D, self._imageTextureID)
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, image.width(), image.height(), 0, GL_RGBA, GL_UNSIGNED_BYTE, image_data)

glActiveTexture(GL_TEXTURE0)
glBindTexture(GL_TEXTURE_2D, self._imageTextureID)

self._program.setUniformValue('texture1', 0)


def paintGL(self):
glBindBuffer(GL_ARRAY_BUFFER, self.bufferID)
glClearColor(0, 0.2, 0.3, 1.0)
glClearDepth(1.0)
glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT)
glDrawArrays(GL_TRIANGLE_STRIP, 0, 6)

def resizeGL(self, w, h):
glViewport(0, 0, w, h)


Not too sure what i'm doing wrong here, but i'm getting back a black rectangle. any ideas?

Answer

Your texture is incomplete. You are not setting filtering and wrap modes. Add these after glTexImage2D:

    glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST )
    glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST )
    glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT )
    glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT )