OpenGL; transparence des png assombrie

glPushMatrix();

glTranslatef(point.x, point.y, 0);
glRotatef(-rotation, 0.0f, 0.0f, 1.0f);
glTranslatef(-point.x, -point.y, 0);

glColor4f(colourFilter[0], colourFilter[1], colourFilter[2], colourFilter[3]);
	
glEnableClientState(GL_TEXTURE_COORD_ARRAY);

glEnable(GL_TEXTURE_2D);

if([texture name] != appDelegate.currentTexture) {
	[appDelegate setCurrentTexture:[texture name]];
	glBindTexture(GL_TEXTURE_2D, [texture name]);
}
	
glVertexPointer(2, GL_FLOAT, 0, qv);

glTexCoordPointer(2, GL_FLOAT, 0, tc);

glEnable(GL_BLEND);

glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);

glDisable(GL_BLEND);
glDisable(GL_TEXTURE_2D);
glDisableClientState(GL_TEXTURE_COORD_ARRAY);

glPopMatrix();

if(lightTransparency) glBlendFunc(GL_ONE, GL_ONE_MINUS_SRC_COLOR);