Drawing textures in OpenGL objective c os x - objective-c

Question

I tried to display a picture, but it is not displayed.
Here is my code for an NSOpenGLView subclass:
//
// MyOpenGLView.m
// OpenGLTests
//
// Created by Tom Schamberger on 10.12.12.
// Copyright (c) 2012 Tom Schamberger. All rights reserved.
//
#import "MyOpenGLView.h"
#implementation MyOpenGLView
- (id)initWithFrame:(NSRect)frame
{
NSOpenGLPixelFormat * pf = [MyOpenGLView basicPixelFormat];
self = [super initWithFrame: frame pixelFormat: pf];
return self;
}
+ (NSOpenGLPixelFormat*) basicPixelFormat
{
NSOpenGLPixelFormatAttribute attributes [] = {
NSOpenGLPFAWindow,
NSOpenGLPFADoubleBuffer, // double buffered
NSOpenGLPFADepthSize, (NSOpenGLPixelFormatAttribute)16, // 16 bit depth buffer
(NSOpenGLPixelFormatAttribute)nil
};
return [[NSOpenGLPixelFormat alloc] initWithAttributes:attributes];
}
- (void) prepareOpenGL
{
glEnable(GL_DEPTH_TEST);
glShadeModel(GL_SMOOTH);
glEnable(GL_CULL_FACE);
glFrontFace(GL_CCW);
glPolygonOffset (1.0f, 1.0f);
glClearColor(0.0f, 0.0f, 0.0f, 0.5f);
if([self loadTextures])
NSLog(#"Load");
}
- (void)drawRect:(NSRect)dirtyRect
{
glClear (GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glBindTexture( GL_TEXTURE_2D, texture);
glPolygonMode(GL_FRONT_AND_BACK,GL_LINE);
glColor3f(1, 1, 1);
glBegin( GL_QUADS );
glTexCoord2f( 0.0f, 0.0f);
glVertex2f( -0.5f, -0.5f);
glTexCoord2f( 1.0f, 0.0f);
glVertex2f( 0.5f, -0.5f);
glTexCoord2f( 1.0f, 1.0f);
glVertex2f( 0.5f, 0.5f);
glTexCoord2f( 0.0f, 1.0f);
glVertex2f( -0.5f, 0.5f);
glEnd();
glFlush();
}
- (BOOL) loadTextures
{
NSImage *img = [NSImage imageNamed:#"NeHe.bmp"];
if(img == nil)
return FALSE;
else if(img.size.height == 0 || img.size.width == 0)
return FALSE;
NSBitmapImageRep *rep = [[NSBitmapImageRep alloc] initWithData: [img TIFFRepresentation]];
glGenTextures( 1, &texture);
glBindTexture( GL_TEXTURE_2D, texture);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_BASE_LEVEL, 0);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAX_LEVEL, 0);
glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR );
glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR );
glTexImage2D( GL_TEXTURE_2D, 0, GL_RGB, rep.size.width,
rep.size.height, 0, GL_RGB,
GL_UNSIGNED_BYTE, rep.bitmapData);
return TRUE;
}
#end
It draws a rectangle, but the texture is not displayed.

Answer 1

You should probably set you clear color alpha to 0.0 rather than 0.5
This code for loading a texture works.
backGroundPath = #"Background.bmp";
NSData* backGroundData = [NSData dataWithContentsOfFile:backGroundPath options:NSUncachedRead error:nil];
backGroundImage = [NSBitmapImageRep imageRepWithData:backGroundData];
glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
glGenTextures( 1, backGroundTexture);
glBindTexture(GL_TEXTURE_2D, backGroundTexture[0]);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER,
GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER,
GL_NEAREST);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, backGroundImage.size.width,
backGroundImage.size.height, 0, GL_RGBA, GL_UNSIGNED_BYTE,
backGroundImage.bitmapData);