View Full Version : Problem loading TGA file (OpenGL SuperBible)

Unresolved External
10-01-2010, 02:45 AM
Hi, I'm currently trying to get the sample program IMAGELOAD from chapter 7 to work from the book OpenGL SuperBible. The problem is in the gltLoadTGA function. I've enclosed the most relevant lines in the code below with "// ========" lines. The function returns NULL after failing to read the file again. I've tried with different TGA-files. Thanx.

GLbyte *gltLoadTGA(const char *szFileName, GLint *iWidth, GLint *iHeight, GLint *iComponents, GLenum *eFormat)
FILE *pFile; // File pointer
TGAHEADER tgaHeader; // TGA file header
unsigned long lImageSize; // Size in bytes of image
short sDepth; // Pixel depth;
GLbyte *pBits = NULL; // Pointer to bits

// Default/Failed values
*iWidth = 0;
*iHeight = 0;
*eFormat = GL_BGR_EXT;
*iComponents = GL_RGB8;

// Attempt to open the fil
pFile = fopen(szFileName, "rb");
if(pFile == NULL)
printf("Error: file not found\n");
return NULL;

// Read in header (binary)
fread(&tgaHeader, /*18*/sizeof(TGAHEADER), 1, pFile);

// Get width, height, and depth of texture
*iWidth = tgaHeader.width;
*iHeight = tgaHeader.height;
sDepth = tgaHeader.bits / 8;

// ================================================== ====
// !!! I wrote this lines myself since the function seems
// to read in the file wrong. Or is it something wrong
// with the order of my struct?!!!
unsigned short temp = tgaHeader.width;
tgaHeader.bits = tgaHeader.height;
tgaHeader.width = tgaHeader.ystart;
tgaHeader.height = temp;
// ================================================== ====

tgaHeader.ystart = 0;


// Put some validity checks here. Very simply, I only understand
// or care about 8, 24, or 32 bit targa's.
if(tgaHeader.bits != 8 && tgaHeader.bits != 24 && tgaHeader.bits != 32)
printf("Error: invalid bitdepth\n");
return NULL;

// Calculate size of image buffer
lImageSize = tgaHeader.width * tgaHeader.height * sDepth;

// Allocate memory and check for success
pBits = (GLbyte*)malloc(lImageSize * sizeof(GLbyte));
if(pBits == NULL)
printf("Error: while allocating\n");
return NULL;

// Read in the bits
// Check for read error. This should catch RLE or other
// weird formats that I don't want to recognize

// ================================================== ====
// !!! The function returns NULL here. Here is the problem !!!
if(fread(pBits, lImageSize, 1, pFile) != 1)
printf("Error: read error\n");
return NULL;
// ================================================== ====

// Set OpenGL format expected
case 3: // Most likely case
*eFormat = GL_BGR_EXT;
*iComponents = GL_RGB8;
case 4:
*eFormat = GL_BGRA_EXT;
*iComponents = GL_RGBA8;
case 1:
*eFormat = GL_LUMINANCE;
*iComponents = GL_LUMINANCE8;

// Done with File

// Return pointer to image data
return pBits;

10-01-2010, 03:01 AM
Are you sure your TGA are in the raw form, and not RLE-compressed ?

Unresolved External
10-04-2010, 06:13 AM
Both the function and the TGA-file are from the book's webpage, so I guess the TGA-file is in the right format. Thanx.

How can I look up if it is in raw-form or RLE-compressed?

10-04-2010, 06:50 AM
Multiply width by height by bytes per pixel; if the result is roughly equal to the file size in bytes then it's raw, otherwise it's most likely compressed (it could also be corrupt, but that's another story).

Unresolved External
10-04-2010, 09:17 AM
So I multiplied the width, height and bytes per pixel and ended up with the same size as the file size, so I guess it's raw then. Now when we know that, what might be the problem?

Since the function is done by the author and he also contributed the TGA-file I find it odd that it's not working.