我正在尝试使用以下方式从加载到 EAGLView 的纹理中获取 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，当我将生成的 UIImage (imageDataPhoto1) 分配给 UIImageView 时，它只是空白的黑色。我应该做点别的吗？顺便说一句，我通过以下方法从相机加载图像作为 EAGLView 的纹理（代码属于 Apple）：
--------来自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;
}