使用UIImage呈现openGL

Question

我使用下面的代码来使用UIImage来呈现openGL。Texture2D类来自苹果，所以我认为它是正确的。图像不显示。我只是得到了由glClearColor制作的背景色。我的应用程序是基于来自苹果的GLpaint示例代码，所以设置是正确的，我能够用openGL绘制线条。

下面的渲染代码是不是遗漏了什么？

- (void) render:(UIImage *)image
{
[EAGLContext setCurrentContext:context];
glViewport(0, 0, backingWidth, backingHeight);

glMatrixMode(GL_PROJECTION);
glLoadIdentity();

// texturing will need these
glEnableClientState(GL_TEXTURE_COORD_ARRAY);
glEnableClientState(GL_VERTEX_ARRAY);
glEnable(GL_TEXTURE_2D);

glOrthof(0, backingWidth, 0, backingHeight, -1, 1);

glMatrixMode(GL_MODELVIEW);

glClearColor(0.2f, 0.2f, 0.2f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

glLoadIdentity();

Texture2D *texture = [[Texture2D alloc] initWithImage:image];

[texture drawInRect: self.frame];


// This application only creates a single color renderbuffer which is already bound at this point.
// This call is redundant, but needed if dealing with multiple renderbuffers.
glBindRenderbuffer(GL_RENDERBUFFER, viewRenderbuffer);
[context presentRenderbuffer:GL_RENDERBUFFER];
}

Answer 1

update：用实际代码替换了原来答案中的坏链接。

下面是对我有用的代码：

-(void) mergeWithImage:(UIImage*) image
{
if(image==nil)
{
    return;
}
glPushMatrix();
glColor4f(256,
          256,
          256,
          1.0);
GLuint stampTexture; // = texture.id;

glBlendFunc(GL_ONE, GL_ONE_MINUS_SRC_ALPHA);
glGenTextures(1, &stampTexture);
glBindTexture(GL_TEXTURE_2D, stampTexture);
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_LINEAR);

GLuint imgwidth = CGImageGetWidth(image.CGImage);
GLuint imgheight = CGImageGetHeight(image.CGImage);
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
void *imageData = malloc( imgheight * imgwidth * 4 );
CGContextRef context2 = CGBitmapContextCreate( imageData, imgwidth, imgheight, 8, 4 * imgwidth, colorSpace, kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Big );
CGContextTranslateCTM (context2, 0, imgheight);
CGContextScaleCTM (context2, 1.0, -1.0);
CGColorSpaceRelease( colorSpace );
CGContextClearRect( context2, CGRectMake( 0, 0, imgwidth, imgheight ) );
CGContextTranslateCTM( context2, 0, imgheight - imgheight );
CGContextDrawImage( context2, CGRectMake( 0, 0, imgwidth, imgheight ), image.CGImage );

glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, imgwidth, imgheight, 0, GL_RGBA, GL_UNSIGNED_BYTE, imageData);

CGContextRelease(context2);

free(imageData);

static const GLfloat texCoords[] = {
    0.0, 1.0,
    1.0, 1.0,
    0.0, 0.0,
    1.0, 0.0
};

glEnableClientState(GL_TEXTURE_COORD_ARRAY);
glTexCoordPointer(2, GL_FLOAT, 0, texCoords);

glEnableClientState(GL_VERTEX_ARRAY);
glEnableClientState(GL_NORMAL_ARRAY);
glEnableClientState(GL_TEXTURE_COORD_ARRAY);

/*
 These arrays would need to be changed if the size of the paintview changes. You must make sure that all image imput is 64x64, 256x256, 512x512 or 1024x1024.  Here we are using 512, but you can use 1024 as follows:

 use the numbers:
 {
 0.0, height, 0.0,
 1024, height, 0.0,
 0.0, height-1024, 0.0,
 1024, height-1024, 0.0
 }
 */

NSLog(@"height of me: %f", self.bounds.size.height);

static const GLfloat vertices[] = {
    0.0,  643, 0.0,
    1024,  643, 0.0,
    0.0, -381, 0.0,
    1024, -381, 0.0
};

static const GLfloat normals[] = {
    0.0, 0.0, 1024,
    0.0, 0.0, 1024,
    0.0, 0.0, 1024,
    0.0, 0.0, 1024
};


glBindTexture(GL_TEXTURE_2D, stampTexture);
glVertexPointer(3, GL_FLOAT, 0, vertices);
glNormalPointer(GL_FLOAT, 0, normals);
glTexCoordPointer(2, GL_FLOAT, 0, texCoords);
glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);

glPopMatrix();

glDeleteTextures( 1, &stampTexture );

// Display the buffer
glBindRenderbufferOES(GL_RENDERBUFFER_OES, viewRenderbuffer);
[context presentRenderbuffer:GL_RENDERBUFFER_OES];

}



-(void) addImageToView{
UIImage* imageToAdd= [UIImage imageNamed:@"IMAGE_TO_ADD_TO_GL_VIEW.png"];


//     all images added to the paining view MUST be 512x512.
//     You can also add smaller images (even transformed ones) using this method - just add it to a UIView and then get it's graphics context

UIView* imageView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 512, 512)];



UIImageView* subView   = [[UIImageView alloc] initWithImage:imageToAdd];


[imageView addSubview:subView];
UIImage* blendedImage =nil;

UIGraphicsBeginImageContext(imageView.frame.size);

[imageView.layer renderInContext:UIGraphicsGetCurrentContext()];

blendedImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

[self mergeWithImage: blendedImage ];