我正在尝试使用来自 Apple 的 GLImageProcessing 示例中的一些 EAGLView 代码对 UIImage 进行一些图像处理。示例代码被配置为对预先安装的图像(Image.png)进行处理。我正在尝试修改代码，以便它接受我选择的 UIImage(或至少 CGImage 数据)并进行处理。问题是，纹理加载器方法 loadTexture()(如下)似乎只接受 C 结构作为参数，而我无法让它接受 UIImage* 或 CGImage 作为参数。有人能给我一个关于如何弥合差距的线索，以便我可以将我的 UIImage 传递到 C 方法中吗？
------------ 来自 Texture.h ---------------
#ifndef TEXTURE_H
#define TEXTURE_H
#include "Imaging.h"
void loadTexture(const char *name, Image *img, RendererInfo *renderer);
#endif /* TEXTURE_H */
----------------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)
{
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 = [UIImage imageNamed:[NSString stringWithUTF8String:name]].CGImage;
rt_assert(CGImage);
if (!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;
}
旁注:以上代码是来自Apple的原始未修改示例代码，编译时不会产生任何错误。但是，当我尝试修改 .h 和 .m 以接受 UIImage* 参数(如下所示)时，编译器会生成以下错误: "Error: expected declaration specifiers or "..."before UIImage"
----------Modified .h 生成编译器错误的代码:-------------
void loadTexture(const char name, Image *img, RendererInfo *renderer, UIImage* newImage)
最佳答案
您可能正在将这个 .h 导入到某个地方的 .c 中。这告诉编译器使用 C 而不是 Objective-C。 UIKit.h(以及它的许多子代码)在 Objective-C 中，不能被 C 编译器编译。
您可以将所有 .c 文件重命名为 .m，但您真正想要的只是使用 CGImageRef 并导入 CGImage.h 。 CoreGraphics 是基于 C 的。 UIKit 是 Objective-C。如果您愿意，Texture.m 在 Objective-C 中没有问题。只需确保 Texture.h 是纯 C 语言。或者(我经常使用 C++ 代码执行此操作)，您可以制作一个 Texture+C.h header ，仅提供您想要公开的 C 安全函数。在Objective-C 代码中导入Texture.h，在C 代码中导入Texture+C.h。或者如果更方便的话，使用 Texture+ObjC.h 将它们命名为其他方式。
关于c++ - 如何获得接受 UIImage 参数的 C 方法？，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/1350108/