Why is texture colour changing in BGL?

Question

I'm loading a texture into a simple GL_QUAD drawn with OpenGL with the help of bgl and bge.texture modules in Blender. The texture loads but the colour of the texture changes, most of the parts are black, blues are rendered red and so on.

Following is the code for loading the texture:

import bge
import bgl
from bge import logic, texture

def loadTex():
    if objbuf is not None:
        bgl.glEnable(bgl.GL_TEXTURE_2D)
        texBuf = bgl.Buffer(bgl.GL_INT, 1)
        bgl.glGenTextures(1, texBuf)
        bgl.glBindTexture(bgl.GL_TEXTURE_2D, texBuf.to_list()[0])
        bgl.glTexImage2D(bgl.GL_TEXTURE_2D, 0, bgl.GL_RGBA, 48, 48, 0,\
            bgl.GL_RGBA, bgl.GL_BYTE, objbuf)
        bgl.glTexParameteri(bgl.GL_TEXTURE_2D, bgl.GL_TEXTURE_MIN_FILTER, \
            bgl.GL_LINEAR)
        bgl.glTexParameteri(bgl.GL_TEXTURE_2D, bgl.GL_TEXTURE_MAG_FILTER, \
            bgl.GL_LINEAR)
        bgl.glBegin(bgl.GL_QUADS);
        bgl.glNormal3f(0, 0, 2)
        bgl.glTexCoord2d(1, 0); bgl.glVertex3f(1, -1, 1.2)
        bgl.glTexCoord2d(0, 0); bgl.glVertex3f(1, 1, 1.2)
        bgl.glTexCoord2d(0, 1); bgl.glVertex3f(-1, 1, 1.2)
        bgl.glTexCoord2d(1, 1); bgl.glVertex3f(-1, -1, 1.2)
        bgl.glEnd()
        bgl.glDeleteTextures(1, texBuf)
        bgl.glDisable(bgl.GL_TEXTURE_2D)

obj = logic.getCurrentController().owner
if not obj.scene.post_draw:
        # face.png is a 48x48 PNG image
        obj["buf"] = texture.imageToArray(texture.ImageFFmpeg(\
            logic.expandPath("//face.png")), "RGBA")
        objbuf = obj["buf"]
        obj.scene.post_draw = [loadTex]

Here is the original image:

and here is the loaded texture:

Excuse the mirroring of texture, I used mirrored textured coordinates. Can anyone help me figure this out? Thanks.

Answer 1

I have solved the problem. In the glTexImage2D call the type parameter(8th) needs to be bgl.GL_UNSIGNED_BYTE instead of bgl.GL_BYTE. It's really strange because when I printed the buffer in console with print(obj["buf"]) the output was

Buffer(GL_BYTE, [...])

Here is the rectified code

import bge
import bgl
from bge import logic, texture

def loadTex():
    if objbuf is not None:
        bgl.glEnable(bgl.GL_TEXTURE_2D)
        bgl.glEnable(bgl.GL_BLEND)
        # enable light because blender disables it if no object is in the vicinity
        bgl.glEnable(bgl.GL_LIGHTING)
        bgl.glBlendFunc(bgl.GL_ONE, bgl.GL_ONE_MINUS_SRC_ALPHA)
        texBuf = bgl.Buffer(bgl.GL_INT, 1)
        bgl.glGenTextures(1, texBuf)
        bgl.glActiveTexture(bgl.GL_TEXTURE0)
        bgl.glBindTexture(bgl.GL_TEXTURE_2D, texBuf.to_list()[0])
        bgl.glTexImage2D(bgl.GL_TEXTURE_2D, 0, bgl.GL_RGBA, 48, 48, 0,\
            bgl.GL_RGBA, bgl.GL_UNSIGNED_BYTE, objbuf)
        bgl.glTexParameteri(bgl.GL_TEXTURE_2D, bgl.GL_TEXTURE_MIN_FILTER, \
            bgl.GL_LINEAR)
        bgl.glTexParameteri(bgl.GL_TEXTURE_2D, bgl.GL_TEXTURE_MAG_FILTER, \
            bgl.GL_LINEAR)
        bgl.glBegin(bgl.GL_QUADS);
        bgl.glNormal3f(0, 0, 1)
        bgl.glTexCoord2d(1, 0); bgl.glVertex3f(1, -1, 1)
        bgl.glTexCoord2d(1, 1); bgl.glVertex3f(1, 1, 1)
        bgl.glTexCoord2d(0, 1); bgl.glVertex3f(-1, 1, 1)
        bgl.glTexCoord2d(0, 0); bgl.glVertex3f(-1, -1, 1)
        bgl.glEnd()
        bgl.glDeleteTextures(1, texBuf)
        bgl.glDisable(bgl.GL_LIGHTING)
        bgl.glDisable(bgl.GL_BLEND)
        bgl.glDisable(bgl.GL_TEXTURE_2D)

obj = logic.getCurrentController().owner
if not obj.scene.post_draw:
        # face.png is a 48x48 PNG image
        obj["buf"] = texture.imageToArray(texture.ImageFFmpeg(\
            logic.expandPath("//face.png")), "RGBA")
        objbuf = obj["buf"]
        obj.scene.post_draw = [loadTex]

Here is the result