C++ OpenGL Texture not loading - c++

Question

void OGLRectangle::LoadTexture(const char* filename)
{
unsigned int texture;
int width, height;
BYTE * data;
FILE * file;
file = fopen(filename, "rb");
width = 1920;
height = 1080;
data = new BYTE[height * width * 3];
fread(data, width * height * 3, 1, file);
fclose(file);
glGenTextures(1.0, &texture);
glBindTexture(GL_TEXTURE_2D, texture);
tex = texture;
glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_NEAREST);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP);
glTexImage2D(GL_TEXTURE_2D, 0, 2, width, height,0, GL_RGB, GL_UNSIGNED_BYTE, data);
delete [] data;
}
I have this code to render in an image, the method is called with:
LoadTexture("C:\\Users\Rhys\Documents\Hills.bmp");
The file exists.
Then I'm trying to render it to the openGL window using;
glEnable(GL_TEXTURE_2D);
glBindTexture(GL_TEXTURE_2D, tex);
glBegin(GL_QUADS);
glTexCoord2d(0.0, 0.0); glVertex2d(0.0, 0.0);
glTexCoord2d(1.0, 0.0); glVertex2d(100.0, 0.0);
glTexCoord2d(1.0, 1.0); glVertex2d(100.0, 100.0);
glTexCoord2d(0.0, 1.0); glVertex2d(0.0, 100.0);
glEnd();
glDisable(GL_TEXTURE_2D);
However, all I'm getting on screen is a darkish blue box, with no texture rendered in it.
I have searched for tutorials on how to do this, even asked my lecturer and I still cannot seem to find out why its not working.
Any help will be greatly appreciated.

Answer 1

The .bmp files loading must be little different
This code simply loads bmp file to memory m_pcbData without compression and indexed color support.
bool CBMPImage::LoadFromFile(const CString& FileName)
{
BITMAPINFOHEADER BitmapInfo;
ZeroMemory(&BitmapInfo, sizeof(BITMAPINFOHEADER));
BITMAPFILEHEADER BitmapFile;
ZeroMemory(&BitmapFile, sizeof(BITMAPFILEHEADER));
std::ifstream FileStream(FileName, std::ios::binary | std::ios::in);
if (!FileStream.good())
return false;
// Read bitmap file info
FileStream.read(reinterpret_cast<char*>(&BitmapFile), sizeof(BITMAPFILEHEADER));
// Read bitmap info
FileStream.read(reinterpret_cast<char*>(&BitmapInfo), sizeof(BITMAPINFOHEADER));
// Proper bitmap file supports only 1 plane
if (BitmapInfo.biPlanes != 1)
return false;
m_cbAlphaBits = 0;
m_cbRedBits = 0;
m_cbGreenBits = 0;
m_cbBlueBits = 0;
// Retrives bits per pixel info
m_cbBitsPerPel = (BMPbyte)BitmapInfo.biBitCount;
// Width and height of image
m_nWidth = BitmapInfo.biWidth;
m_nHeight = BitmapInfo.biHeight;
// Compute bitmap file size
m_nSize = 4 * ((m_nWidth * m_cbBitsPerPel + 31) / 32) * m_nHeight;
// Less important info
m_nPixelWidthPerMeter = BitmapInfo.biXPelsPerMeter;
m_nPixelHeightPerMeter = BitmapInfo.biYPelsPerMeter;
// Indexes info not important in our case
m_nClrCount = BitmapInfo.biClrUsed;
m_nClrImportant = BitmapInfo.biClrImportant;
// COMPRESSION MUST BE BI_RGB
m_Compression = (BMPCompression)BitmapInfo.biCompression;
delete [] m_pcbData;
m_pcbData = NULL;
// Allocate proper data size
m_pcbData = new BMPbyte[m_nSize];
// Read actual image data, considering offset of file header
FileStream.seekg(BitmapFile.bfOffBits);
FileStream.read(reinterpret_cast<char*>(m_pcbData), m_nSize);
FileStream.close();
return true;
}
than load bmp texture data to OpenGL
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, Image.GetWidth(), Image.GetHeight(), 0, GL_BGR_EXT, GL_UNSIGNED_BYTE, (GLvoid*)Image.GetImageData());
GL_BGR_EXT is important because bmp stores image data in reverse byte order.
Secondly you must specify your material color as white because of usage that texture environment GL_TEXTURE_ENV_MODE, GL_MODULATE
And as mentioned #Reto Koradi, you must specify to generate mipmaps before texture image loading using one of these function calls.
glGenerateMipmap(GL_TEXTURE_2D);
or
glTexParameteri(GL_TEXTURE_2D, GL_GENERATE_MIPMAP, GL_TRUE);
Plus as you used not power of two textures (width = 1920;
height = 1080;) it may not work.

Answer 2

You're setting the attribute to sample with mipmaps:
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_NEAREST);
You should only set that if your textures actually has mipmaps. To generate mipmaps, you can call:
glGenerateMipmap(GL_TEXTURE_2D);
after the glTexImage2D() call. Or you can simply set the sampler attribute to not use mipmaps:
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
As has already been pointed out: If your image file is indeed a BMP, and not just a raw image file, your image loading code will also need work.