我正在尝试使用make命令编译项目。 我有几个关于命名空间std ::的错误。 我正在使用Ubuntu，我想我已经安装了编译C ++语言所需的全部内容。
以下是代码：
#include "texture.hpp"
#include "texturefetch.hpp"
#include <png.h>
#include <cstdio>
#include <iostream>
#include <cmath>
#include <assert.h>
#include <string>
Texture::~Texture(){
delete[] mPixels;
for (int i=1; i<mlodmax+1; ++i)
delete[] mMipMapLevels[i];
delete[] mMipMapLevels;
}
bool Texture::getclamp() const
{
return clamp;
}
void Texture::setclamp(bool value)
{
clamp = value;
}
int Texture::load(std::string filename){
FILE *fp;
png_byte magic[8];
/* open image file */
fp = std::fopen (filename.c_str(), "rb");
if (!fp) {
fprintf (stderr, "error: couldn't open \"%s\"!\n", filename.c_str());
return 0;
}
/* read magic number */
fread (magic, 1, sizeof (magic), fp);
/* check for valid magic number */
if (!png_check_sig (magic, sizeof (magic))) {
fprintf (stderr, "error: \"%s\" is not a valid PNG image!\n", filename.c_str());
fclose (fp);
return 0;
}
/* create a png read struct */
png_structp png_ptr = png_create_read_struct (PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
if (!png_ptr) {
fclose (fp);
return 0;
}
/* create a png info struct */
png_infop info_ptr = png_create_info_struct (png_ptr);
if (!info_ptr) {
fclose (fp);
png_destroy_read_struct (&png_ptr, NULL, NULL);
return 0;
}
/* initialize the setjmp for returning properly after a libpng
error occured */
if (setjmp (png_jmpbuf (png_ptr))) {
fclose (fp);
png_destroy_read_struct (&png_ptr, &info_ptr, NULL);
return 0;
}
/* setup libpng for using standard C fread() function
with our FILE pointer */
png_init_io (png_ptr, fp);
/* tell libpng that we have already read the magic number */
png_set_sig_bytes (png_ptr, sizeof (magic));
/* read png info */
png_read_info (png_ptr, info_ptr);
int bit_depth, color_type;
/* get some usefull information from header */
bit_depth = png_get_bit_depth (png_ptr, info_ptr);
color_type = png_get_color_type (png_ptr, info_ptr);
/* convert index color images to RGB images */
if (color_type == PNG_COLOR_TYPE_PALETTE)
png_set_palette_to_rgb (png_ptr);
/* convert 1-2-4 bits grayscale images to 8 bits
grayscale. */
if (color_type == PNG_COLOR_TYPE_GRAY && bit_depth < 8)
png_set_expand_gray_1_2_4_to_8(png_ptr);
if (png_get_valid (png_ptr, info_ptr, PNG_INFO_tRNS))
png_set_tRNS_to_alpha (png_ptr);
if (bit_depth == 16)
png_set_strip_16 (png_ptr);
else if (bit_depth < 8)
png_set_packing (png_ptr);
/* update info structure to apply transformations */
png_read_update_info (png_ptr, info_ptr);
/* retrieve updated information */
png_get_IHDR (png_ptr, info_ptr,
(png_uint_32*)(&mWidth),
(png_uint_32*)(&mHeight),
&bit_depth, &color_type,
NULL, NULL, NULL);
switch (color_type) {
case PNG_COLOR_TYPE_GRAY:
mPixelFormat = 1;
break;
case PNG_COLOR_TYPE_GRAY_ALPHA:
mPixelFormat = 2;
break;
case PNG_COLOR_TYPE_RGB:
mPixelFormat = 3;
break;
case PNG_COLOR_TYPE_RGB_ALPHA:
mPixelFormat = 4;
break;
default:
/* Badness */
break;
}
/* we can now allocate memory for storing pixel data */
mPixels = new unsigned char[mWidth * mHeight * mPixelFormat];
png_bytep *row_pointers;
/* setup a pointer array. Each one points at the begening of a row. */
row_pointers = new png_bytep[mHeight];
for (int i = 0; i < mHeight; ++i) {
row_pointers[i] = (png_bytep)(mPixels +
((mHeight - (i + 1)) * mWidth * mPixelFormat));
}
/* read pixel data using row pointers */
png_read_image (png_ptr, row_pointers);
/* finish decompression and release memory */
png_read_end (png_ptr, NULL);
png_destroy_read_struct (&png_ptr, &info_ptr, NULL);
fclose (fp);
/* we don't need row pointers anymore */
delete[] row_pointers;
return 1;
}
Texture::Texture(std::string filename) : mPixels(NULL), mMipMapLevels(NULL), hasmipmap(false), mSu(1.f), mSv(1.f), clamp(false){
if (!load(filename)) {
std::cerr << "Erreur : impossible de lire le fichier " << filename << std::endl;
} else {
mlodmax = (int)std::floor(std::min(std::log2(mWidth), std::log2(mHeight)));
}
}
bool Texture::prefilter(){
hasmipmap = buildmipmaps();
return hasmipmap;
}
bool Texture::buildmipmaps(){
mMipMapLevels = new unsigned char*[mlodmax+1];
mMipMapLevels[0] = mPixels;
for (int i=1;i<mlodmax+1; ++i)
mMipMapLevels[i]=NULL;
// Call of the student function
return prefilterTexture(mMipMapLevels, mWidth, mHeight, mPixelFormat, mlodmax+1);
}
void Texture::setScale(float su, float sv){
mSu = 1.f/su;
mSv = 1.f/sv;
}
void Texture::getPixel(float u, float v, float lod, Color &color){
if (clamp){
u = (u>0) ? ((u<1) ? u : 1) : 0;
v = (v>0) ? ((v<1) ? v : 1) : 0;
}
u = mSu*u;
v = mSv*v;
float scaledU = u * (mWidth - 1);
float scaledV = v * (mHeight - 1);
// color = Color(u,v,0);
// return;
int s = ((int)scaledU) % mWidth;
int t = ((int)scaledV) % mHeight;
float ds = scaledU - std::floor(scaledU);
float dt = scaledV - std::floor(scaledV);
if (s<0){
s = s+mWidth;
}
if (t<0){
t = t+mHeight;
}
// Nearest
// color = interpolate(mPixels, mWidth, mHeight, s,t, 0.f,0.f);
// return;
// Linear
// color = interpolate(mPixels, mWidth, mHeight, s,t, ds, dt);
// return;
/* Filtrage */
lod = std::min(lod-1, (float)mlodmax);
if (lod > 0) {
// color = Color(0, std::floor(lod), 0);
// return;
int baselod = (int)std::floor(lod);
int pix = (int)(std::pow(2.f,baselod)); // bigger inferior mipmap level
if (hasmipmap){
// Sous-echantillonnage --> filtrage mip-map
Color color1 = integrateMipMap(baselod, ((float)s + ds)/pix, ((float)t + dt)/pix, mWidth/pix, mHeight/pix);
if (baselod < mlodmax){
pix = std::pow(2.f,baselod+1); // smaller superior mipmap level
Color color2 = integrateMipMap(baselod+1, ((float)s + ds)/pix, ((float)t + dt)/pix, mWidth/pix, mHeight/pix);
float dm = lod - std::floor(lod);
color = color1 * (1-dm) + color2 * dm;
} else {
color = color1;
}
} else {
int cs = pix * (s/pix);
int ct = pix * (t/pix);
Color color1 = integrateExplicit(mMipMapLevels[0], mWidth, mHeight, mPixelFormat, cs, ct, pix, pix);
if (baselod < mlodmax){
pix = std::pow(2.f,baselod+1); // smaller superior mipmap level
cs = pix * (s/pix);
ct = pix * (t/pix);
Color color2 = integrateExplicit(mMipMapLevels[0], mWidth, mHeight, mPixelFormat, cs, ct, pix, pix);
float dm = lod - std::floor(lod);
color = color1 * (1-dm) + color2 * dm;
} else {
color = color1;
}
}
} else {
// color = Color(1/*fabsf(lod)*/, 0, 0);
// return;
color = interpolate(mPixels, mWidth, mHeight, s,t, ds,dt);
}
}
Color Texture::integrateMipMap(int level, float s, float t, int w, int h){
Color color(0.f, 0.f, 0.f);
color = interpolate(mMipMapLevels[level], w, h, (int)s, (int)t, s-std::floor(s), t-std::floor(t));
return color;
}
Color Texture::integrateExplicit(unsigned char *pixels, int imageWidth, int imageHeight, int pixelFormat, float s, float t, int w, int h){
#if 0
Color color(0.f, 0.f, 0.f);
for (int i=0; i<h; i++)
for (int j=0; j<w; j++) {
int k = ((int)(t+i)) % imageHeight;
int l = ((int)(s+j)) % imageWidth;
int linPos = (k*imageWidth + l)*(pixelFormat);
Color centerColor(((float) pixels[linPos])/255.0, ((float) pixels[linPos+1])/255.0, ((float) pixels[linPos+2])/255.0);
color = color + centerColor;
}
color = color * (1.f/(w*h));
return color;
#endif
// Call of the student function
return integrateTexture(pixels, imageWidth, imageHeight, pixelFormat, s, t, w, h);
}
Color Texture::interpolate(unsigned char *pixels, int w, int h, int s, int t, float ds, float dt){
#if 0
Color color;
// Sur échantillonnage --> interpolation
// nearest texel
int linPos = (t*w + s)*(mPixelFormat);
Color centerColor(((float) pixels[linPos])/255.0, ((float) pixels[linPos+1])/255.0, ((float) pixels[linPos+2])/255.0);
Color rightColor;
int r = std::min(s+1, w-1);
int posds = (t*w + r)*(mPixelFormat);
rightColor = Color(
((float) pixels[posds])/255.0,
((float) pixels[posds+1])/255.0,
((float) pixels[posds+2])/255.0
);
Color upColor;
int p = std::min(t+1, h-1);
int posdt = (p*w + s)*(mPixelFormat);
upColor = Color (
((float) pixels[posdt])/255.0,
((float) pixels[posdt+1])/255.0,
((float) pixels[posdt+2])/255.0
);
Color upRightColor;
int posdtds = (p*w + r)*(mPixelFormat);
upRightColor = Color (
((float) pixels[posdtds])/255.0,
((float) pixels[posdtds+1])/255.0,
((float) pixels[posdtds+2])/255.0
);
rightColor = centerColor*(1-ds) + rightColor*ds;
upColor = upColor*(1-ds) + upRightColor*ds;
color = rightColor*(1-dt) + upColor*dt;
return color;
#endif
// Call of the student function
return interpolateTexture(pixels, w, h, mPixelFormat, (float)s+ds, (float)t+dt);
}
这是终端中的错误：
In file included from /home/celine/OIM-LancerDeRayons-2014/coreraytracer/texture.cpp:1:0:
/home/celine/OIM-LancerDeRayons-2014/coreraytracer/texture.hpp: In member function ‘float Texture::computeMipmapLevel(const Vector3D&, const Vector3D&)’:
/home/celine/OIM-LancerDeRayons-2014/coreraytracer/texture.hpp:55:16: error: ‘log2’ is not a member of ‘std’
return std::log2(std::max(dTdx.norm()*width()*mSu, dTdy.norm()*height()*mSv));
^
/home/celine/OIM-LancerDeRayons-2014/coreraytracer/texture.hpp:55:16: note: suggested alternative:
In file included from /usr/include/features.h:374:0,
from /usr/include/x86_64-linux-gnu/c++/4.8/bits/os_defines.h:39,
from /usr/include/x86_64-linux-gnu/c++/4.8/bits/c++config.h:426,
from /usr/include/c++/4.8/cmath:41,
from /home/celine/OIM-LancerDeRayons-2014/coreraytracer/vector3d.hpp:3,
from /home/celine/OIM-LancerDeRayons-2014/coreraytracer/texture.hpp:4,
from /home/celine/OIM-LancerDeRayons-2014/coreraytracer/texture.cpp:1:
/usr/include/x86_64-linux-gnu/bits/math-finite.h:344:15: note: ‘log2’
extern double __REDIRECT_NTH (log2, (double), __log2_finite);
^
/home/celine/OIM-LancerDeRayons-2014/coreraytracer/texture.cpp: In constructor ‘Texture::Texture(std::string)’:
/home/celine/OIM-LancerDeRayons-2014/coreraytracer/texture.cpp:162:44: error: ‘log2’ is not a member of ‘std’
mlodmax = (int)std::floor(std::min(std::log2(mWidth), std::log2(mHeight)));
^
/home/celine/OIM-LancerDeRayons-2014/coreraytracer/texture.cpp:162:44: note: suggested alternative:
In file included from /usr/include/features.h:374:0,
from /usr/include/x86_64-linux-gnu/c++/4.8/bits/os_defines.h:39,
from /usr/include/x86_64-linux-gnu/c++/4.8/bits/c++config.h:426,
from /usr/include/c++/4.8/cmath:41,
from /home/celine/OIM-LancerDeRayons-2014/coreraytracer/vector3d.hpp:3,
from /home/celine/OIM-LancerDeRayons-2014/coreraytracer/texture.hpp:4,
from /home/celine/OIM-LancerDeRayons-2014/coreraytracer/texture.cpp:1:
/usr/include/x86_64-linux-gnu/bits/math-finite.h:344:15: note: ‘log2’
extern double __REDIRECT_NTH (log2, (double), __log2_finite);
^
/home/celine/OIM-LancerDeRayons-2014/coreraytracer/texture.cpp:162:63: error: ‘log2’ is not a member of ‘std’
mlodmax = (int)std::floor(std::min(std::log2(mWidth), std::log2(mHeight)));
^
/home/celine/OIM-LancerDeRayons-2014/coreraytracer/texture.cpp:162:63: note: suggested alternative:
In file included from /usr/include/features.h:374:0,
from /usr/include/x86_64-linux-gnu/c++/4.8/bits/os_defines.h:39,
from /usr/include/x86_64-linux-gnu/c++/4.8/bits/c++config.h:426,
from /usr/include/c++/4.8/cmath:41,
from /home/celine/OIM-LancerDeRayons-2014/coreraytracer/vector3d.hpp:3,
from /home/celine/OIM-LancerDeRayons-2014/coreraytracer/texture.hpp:4,
from /home/celine/OIM-LancerDeRayons-2014/coreraytracer/texture.cpp:1:
/usr/include/x86_64-linux-gnu/bits/math-finite.h:344:15: note: ‘log2’
extern double __REDIRECT_NTH (log2, (double), __log2_finite);
我看了一下互联网，我试图包括但是它仍然无法正常工作......
谢谢！
答案 0 :(得分：3)
log2是C99功能。它不在C ++ 98中，因此不在std命名空间中。在C ++ 11模式下编译（C ++ 11与C99对齐）：
// g++ -std=c++11
#include <cmath>
#include <iostream>
int main()
{
std::cout << std::log2(3) << std::endl;
}
...或者从C头获取函数，没有命名空间：
// g++ -std=c++98
#include <iostream>
#include <math.h>
int main()
{
std::cout << log2(3) << std::endl;
}