How to get method C to accept UIImage parameter?

Question

I am trying to do some image processing on UIImage using some EAGLView code from Apple's GLImageProcessing sample. The sample code is configured to process a predefined image (Image.png). I am trying to modify the code so that it accepts the UIImage (or at least the CGImage data) of my choice and processes this. The problem is that the loadTexture () method (for example, texture-loader) of the texture-loader only accepts C-structures as parameters, and I could not get it to accept UIImage * or CGImage as a parameter. Can someone let me know how to bridge the gap so that I can pass my UIImage to the C method?

------------ from Texture.h ---------------

#ifndef TEXTURE_H
#define TEXTURE_H

#include "Imaging.h"


void loadTexture(const char *name, Image *img, RendererInfo *renderer);

#endif /* TEXTURE_H */

---------------- 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)
{
    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;
}

Side Note: The above code is Apple's original and unmodified code sample and does not generate compilation errors. However, when I try to change .h and .m to accept the UIImage * parameter (as shown below), the compiler generates the following error: "Error: expected declaration qualifiers or" ... "before UIImage"

---------- Modified .h code that generates a compiler error: -------------

void loadTexture(const char name, Image *img, RendererInfo *renderer, UIImage* newImage)

Answer 1

, .h .c -. C, Objective-C. UIKit.h ( ) Objective-C C.

.c .m, , , CGImageRef CGImage.h. CoreGraphics C-based. UIKit - Objective-C. , , Texture.m Objective-C. , Texture.h C. ( ++), Texture+C.h, C-safe, . Texture.h Objective-C Texture+C.h C. , , Texture+ObjC.h.

Answer 2

, UIKit.

Answer 3

Why are you transferring a new loadTexture image instead of loading your own LoadTexture UI loading in order to open the new image you want?

LoadTexture:

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;


[Why not have the following fetch your UIImage?]


    CGImageRef CGImage = [UIImage imageNamed:[NSString stringWithUTF8String:name]].CGImage;
    rt_assert(CGImage);
    if (!CGImage)
        return;