如何将OpenGL视图捕获为UIImage？

问题描述

| 当我尝试使用此方法将OpenGL视图转换为UIImage时，仅返回视图的背景，而不返回GLView内容。如何将OpenGL的上下文转换为UIImage？     

解决方法

        使用下面的代码在

UIImage

中转换

opengl

视图。

GLubyte *buffer = (GLubyte *) malloc(backingWidth * backingHeight * 4);
 GLubyte *buffer2 = (GLubyte *) malloc(backingWidth * backingHeight * 4);
 GLvoid *pixel_data = nil;
 glReadPixels(0,backingWidth,backingHeight,GL_RGBA,GL_UNSIGNED_BYTE,(GLvoid *)buffer);
for (int y=0; y<backingHeight; y++) {
     for (int x=0; x<backingWidth*4; x++) {
         buffer2[y * 4 * backingWidth + x] =
     buffer[(backingHeight - y - 1) * backingWidth * 4 + x];
     }
 }
 CGDataProviderRef provider;
 provider = CGDataProviderCreateWithData(NULL,buffer2,backingWidth * backingHeight * 4,freeImageData);
 // set up for CGImage creation
 int bitsPerComponent = 8;
 int bitsPerPixel = 32;
 int bytesPerRow = 4 * backingWidth;
 CGColorSpaceRef colorSpaceRef = CGColorSpaceCreateDeviceRGB();
 CGBitmapInfo bitmapInfo = kCGBitmapByteOrderDefault;
 // Use this to retain alpha
 //CGBitmapInfo bitmapInfo = kCGImageAlphaPremultipliedLast;
 CGColorRenderingIntent renderingIntent = kCGRenderingIntentDefault;
 CGImageRef imageRef = CGImageCreate(backingWidth,bitsPerComponent,bitsPerPixel,bytesPerRow,colorSpaceRef,bitmapInfo,provider,NULL,NO,renderingIntent);
 // this contains our final image.
 UIImage *newUIImage = [UIImage imageWithCGImage:imageRef];

摘自     ,        这取决于您使用的OpenGL视图。从iOS 5开始，您可以使用GLKit和相应的GLKView来大大简化呈现UIImage的过程。

GLKView* v = (GLKView*) _previewViewController.view;
UIImage* thumbnail = [v snapshot];

http://developer.apple.com/library/ios/#documentation/GLkit/Reference/GLKView_ClassReference/Reference/Reference.html     ,        感谢您的代码。我发现它很有用，但我不得不添加一些额外的代码以正确释放带有缓冲区，buffer2，imageRef，colorSpaceRef和提供程序指针的分配的内存。请注意，buffer2是使用提供程序释放功能释放的。

static void myProviderReleaseData (void *info,const void *data,size_t size)
{
    free((void*)data);
}

- (UIImage*)renderToImage
{
    // The image size should be grabbed from your ESRenderer class. 
    // That parameter is get in renderer function: 
    // - (BOOL) resizeFromLayer:(CAEAGLLayer *)layer {
    // glGetRenderbufferParameterivOES(GL_RENDERBUFFER_OES,GL_RENDERBUFFER_WIDTH_OES,&backingWidth);
    GLint backingWidth = renderer.backingWidth;
    GLint backingHeight = renderer.backingHeight;

    GLubyte *buffer = (GLubyte *) malloc(backingWidth * backingHeight * 4);
    GLubyte *buffer2 = (GLubyte *) malloc(backingWidth * backingHeight * 4);

    glReadPixels(0,(GLvoid *)buffer);
    for (int y=0; y<backingHeight; y++) {
        for (int x=0; x<backingWidth*4; x++) {
            buffer2[y * 4 * backingWidth + x] =
            buffer[(backingHeight - y - 1) * backingWidth * 4 + x];
        }
    }
    free(buffer);
    CGDataProviderRef provider = CGDataProviderCreateWithData(NULL,myProviderReleaseData);
    // set up for CGImage creation
    int bitsPerComponent = 8;
    int bitsPerPixel = 32;
    int bytesPerRow = 4 * backingWidth;
    CGColorSpaceRef colorSpaceRef = CGColorSpaceCreateDeviceRGB();
    // Use this to retain alpha
    CGBitmapInfo bitmapInfo = kCGImageAlphaPremultipliedLast;
    CGColorRenderingIntent renderingIntent = kCGRenderingIntentDefault;
    CGImageRef imageRef = CGImageCreate(backingWidth,renderingIntent);
    // this contains our final image.
    UIImage *newUIImage = [UIImage imageWithCGImage:imageRef];
    CGImageRelease(imageRef);
    CGColorSpaceRelease(colorSpaceRef);
    CGDataProviderRelease(provider);

    return newUIImage;
}