如何從EAGLView的紋理獲取UIImage？

我想從我用下面的方式加載到EAGLView紋理一個UIImage：如何從EAGLView的紋理獲取UIImage？

//Try to get UIImage from EAGLView and assign to imageDataPhoto1 

UIGraphicsBeginImageContext(myEAGLView.bounds.size); 
[myEAGLView.layer renderInContext:UIGraphicsGetCurrentContext()]; 
imageDataPhoto1 = UIGraphicsGetImageFromCurrentImageContext(); 
UIGraphicsEndImageContext(); 

[imageDataPhoto1 retain];

不幸的是，當我分配造成的UIImage（imageDataPhoto1）到一個UIImageView它只是空白的黑色。我應該做其他事嗎？順便說一句，我從相機加載一個圖像，以EAGLView的紋理在以下方法（代碼屬於Apple）：

------- from Texture.m -------

#import <UIKit/UIKit.h> 
#import "Texture.h" 


static unsigned int nextPOT(unsigned int x) 
{ 
    x = x - 1; 
    x = x | (x >> 1); 
    x = x | (x >> 2); 
    x = x | (x >> 4); 
    x = x | (x >> 8); 
    x = x | (x >>16); 
    return x + 1; 
} 


// This is not a fully generalized image loader. It is an example of how to use 
// CGImage to directly access decompressed image data. Only the most commonly 
// used image formats are supported. It will be necessary to expand this code 
// to account for other uses, for example cubemaps or compressed textures. 
// 
// If the image format is supported, this loader will Gen a OpenGL 2D texture object 
// and upload texels from it, padding to POT if needed. For image processing purposes, 
// border pixels are also replicated here to ensure proper filtering during e.g. blur. 
// 
// The caller of this function is responsible for deleting the GL texture object. 
void loadTexture(const char *name, Image *img, RendererInfo *renderer, CGImageRef newImage) 
{ 
    GLuint texID = 0, components, x, y; 
    GLuint imgWide, imgHigh;  // Real image size 
    GLuint rowBytes, rowPixels; // Image size padded by CGImage 
    GLuint POTWide, POTHigh;  // Image size padded to next power of two 
    CGBitmapInfo info;   // CGImage component layout info 
    CGColorSpaceModel colormodel; // CGImage colormodel (RGB, CMYK, paletted, etc) 
    GLenum internal, format; 
    GLubyte *pixels, *temp = NULL; 

    CGImageRef CGImage = newImage; 
    rt_assert(CGImage); 
    if (!CGImage){ 
     NSLog(@"No CGImage!"); 
    return; 
    } 

    // Parse CGImage info 
    info  = CGImageGetBitmapInfo(CGImage);  // CGImage may return pixels in RGBA, BGRA, or ARGB order 
    colormodel = CGColorSpaceGetModel(CGImageGetColorSpace(CGImage)); 
    size_t bpp = CGImageGetBitsPerPixel(CGImage); 
    if (bpp < 8 || bpp > 32 || (colormodel != kCGColorSpaceModelMonochrome && colormodel != kCGColorSpaceModelRGB)) 
    { 
     // This loader does not support all possible CGImage types, such as paletted images 
     CGImageRelease(CGImage); 
     return; 
    } 
    components = bpp>>3; 
    rowBytes = CGImageGetBytesPerRow(CGImage); // CGImage may pad rows 
    rowPixels = rowBytes/components; 
    imgWide = CGImageGetWidth(CGImage); 
    imgHigh = CGImageGetHeight(CGImage); 
    img->wide = rowPixels; 
    img->high = imgHigh; 
    img->s  = (float)imgWide/rowPixels; 
    img->t  = 1.0; 

    // Choose OpenGL format 
    switch(bpp) 
    { 
     default: 
      rt_assert(0 && "Unknown CGImage bpp"); 
     case 32: 
     { 
      internal = GL_RGBA; 
      switch(info & kCGBitmapAlphaInfoMask) 
      { 
       case kCGImageAlphaPremultipliedFirst: 
       case kCGImageAlphaFirst: 
       case kCGImageAlphaNoneSkipFirst: 
        format = GL_BGRA; 
        break; 
       default: 
        format = GL_RGBA; 
      } 
      break; 
     } 
     case 24: 
      internal = format = GL_RGB; 
      break; 
     case 16: 
      internal = format = GL_LUMINANCE_ALPHA; 
      break; 
     case 8: 
      internal = format = GL_LUMINANCE; 
      break; 
    } 

    // Get a pointer to the uncompressed image data. 
    // 
    // This allows access to the original (possibly unpremultiplied) data, but any manipulation 
    // (such as scaling) has to be done manually. Contrast this with drawing the image 
    // into a CGBitmapContext, which allows scaling, but always forces premultiplication. 
    CFDataRef data = CGDataProviderCopyData(CGImageGetDataProvider(CGImage)); 
    rt_assert(data); 
    pixels = (GLubyte *)CFDataGetBytePtr(data); 
    rt_assert(pixels); 

    // If the CGImage component layout isn't compatible with OpenGL, fix it. 
    // On the device, CGImage will generally return BGRA or RGBA. 
    // On the simulator, CGImage may return ARGB, depending on the file format. 
    if (format == GL_BGRA) 
    { 
     uint32_t *p = (uint32_t *)pixels; 
     int i, num = img->wide * img->high; 

     if ((info & kCGBitmapByteOrderMask) != kCGBitmapByteOrder32Host) 
     { 
      // Convert from ARGB to BGRA 
      for (i = 0; i < num; i++) 
       p[i] = (p[i] << 24) | ((p[i] & 0xFF00) << 8) | ((p[i] >> 8) & 0xFF00) | (p[i] >> 24); 
     } 

     // All current iPhoneOS devices support BGRA via an extension. 
     if (!renderer->extension[IMG_texture_format_BGRA8888]) 
     { 
      format = GL_RGBA; 

      // Convert from BGRA to RGBA 
      for (i = 0; i < num; i++) 
#if __LITTLE_ENDIAN__ 
       p[i] = ((p[i] >> 16) & 0xFF) | (p[i] & 0xFF00FF00) | ((p[i] & 0xFF) << 16); 
#else 
      p[i] = ((p[i] & 0xFF00) << 16) | (p[i] & 0xFF00FF) | ((p[i] >> 16) & 0xFF00); 
#endif 
     } 
    } 

    // Determine if we need to pad this image to a power of two. 
    // There are multiple ways to deal with NPOT images on renderers that only support POT: 
    // 1) scale down the image to POT size. Loses quality. 
    // 2) pad up the image to POT size. Wastes memory. 
    // 3) slice the image into multiple POT textures. Requires more rendering logic. 
    // 
    // We are only dealing with a single image here, and pick 2) for simplicity. 
    // 
    // If you prefer 1), you can use CoreGraphics to scale the image into a CGBitmapContext. 
    POTWide = nextPOT(img->wide); 
    POTHigh = nextPOT(img->high); 

    if (!renderer->extension[APPLE_texture_2D_limited_npot] && (img->wide != POTWide || img->high != POTHigh)) 
    { 
     GLuint dstBytes = POTWide * components; 
     GLubyte *temp = (GLubyte *)malloc(dstBytes * POTHigh); 

     for (y = 0; y < img->high; y++) 
      memcpy(&temp[y*dstBytes], &pixels[y*rowBytes], rowBytes); 

     img->s *= (float)img->wide/POTWide; 
     img->t *= (float)img->high/POTHigh; 
     img->wide = POTWide; 
     img->high = POTHigh; 
     pixels = temp; 
     rowBytes = dstBytes; 
    } 

    // For filters that sample texel neighborhoods (like blur), we must replicate 
    // the edge texels of the original input, to simulate CLAMP_TO_EDGE. 
    { 
     GLuint replicatew = MIN(MAX_FILTER_RADIUS, img->wide-imgWide); 
     GLuint replicateh = MIN(MAX_FILTER_RADIUS, img->high-imgHigh); 
     GLuint imgRow = imgWide * components; 

     for (y = 0; y < imgHigh; y++) 
      for (x = 0; x < replicatew; x++) 
       memcpy(&pixels[y*rowBytes+imgRow+x*components], &pixels[y*rowBytes+imgRow-components], components); 
     for (y = imgHigh; y < imgHigh+replicateh; y++) 
      memcpy(&pixels[y*rowBytes], &pixels[(imgHigh-1)*rowBytes], imgRow+replicatew*components); 
    } 

    if (img->wide <= renderer->maxTextureSize && img->high <= renderer->maxTextureSize) 
    { 
     glGenTextures(1, &texID); 
     glBindTexture(GL_TEXTURE_2D, texID); 
     // Set filtering parameters appropriate for this application (image processing on screen-aligned quads.) 
     // Depending on your needs, you may prefer linear filtering, or mipmap generation. 
     glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST); 
     glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST); 
     glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE); 
     glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE); 
     glTexImage2D(GL_TEXTURE_2D, 0, internal, img->wide, img->high, 0, format, GL_UNSIGNED_BYTE, pixels); 
    } 

    if (temp) free(temp); 
    CFRelease(data); 
    CGImageRelease(CGImage); 
    img->texID = texID; 
}

來源

2009-08-29 RexOnRoids