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Loading bitmaps/targas in OpenGL


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#1 Viscous-Flow   Members   -  Reputation: 122

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Posted 03 September 2001 - 12:34 PM

Ok, I have tried time and time again. I have written a basic load bitmap function and load targa function, but they both don''t work at all. I''ll post the code and see if you can help me. GLImage class definition: (look at the IMAGE struct I made since that is important too)
#ifndef GLIMAGE
#define GLIMAGE

//  Define the universal bitmap id
#define BITMAP_ID 0x4D42

#include "stdio.h"	//  Holds the file manipulation routines

//  Structure that holds pertinent information about image formats
typedef struct
{
	short int		width;		//  Width of the image
	short int		height;		//  Height of the image
	unsigned char	*data;		//  Data of the image
} IMAGE;

//  The definition fo the GLImage class
class GLImage
{
	private:
		FILE				*file;				//  The file pointer

		//  Bitmap variables
		IMAGE				*bmpImage;			//  Structure that holds pertinent information about the Windows bitmap format
		BITMAPFILEHEADER	bitmapFileHeader;	//  The bitmap file header
		BITMAPINFOHEADER	bitmapInfoHeader;	//  The bitmap information header

		//  Targa variables
		IMAGE				*tgaImage;			//  Structure that holds pertinent information about the Targa image format
		unsigned char		imageTypeCode;		//  The image type (i.e. 1, 2, or 3)
		unsigned char		bitCount;			//  The bit count of the Targa image
		unsigned char		ucharBad;			//  Garbage unsigned char data
		short int			sintBad;			//  Garbage short int data
		long				imageSize;			//  Size of the TGA image
		int					colorMode;			//  Holds color mode - 4 for RGBA  - 3 for RGB

	public:
		//  Loads a Windows bitmap file
		IMAGE* LoadBMPFile(char *filename);

		//  Loads a Targa image format file
		IMAGE* LoadTGAFile(char *filename);
};

#endif
Ok that was the class, here are the function declerations:
//  Include neccessary header files
#include "stdafx.h"		//  Header file for Windows
#include "GLImage.h"	//  Header file for the GLImage class

//  Loads a Windows bitmap file
IMAGE* GLImage::LoadBMPFile(char* filename)
{
	//  Open the filename in "read binary" mode
	file = fopen(filename, "rb");

	//  If the file couldn''t be opened return NULL
	if(file == NULL)
		return NULL;

	//  Read the bitmap file header
	fread(&bitmapFileHeader, sizeof(BITMAPFILEHEADER), 1, file);

	//  Verify that this is a bitmap by checking for the universal bitmap ID
	if(bitmapFileHeader.bfType != BITMAP_ID)
	{
		//  This is not a bitmap so close the file and return NULL
		fclose(file);

		return NULL;
	}

	//  Read the bitmap information header
	fread(&bitmapInfoHeader, sizeof(BITMAPINFOHEADER), 1, file);

	//  Move the file pointer to the beginning of the bitmap data
	fseek(file, bitmapFileHeader.bfOffBits, SEEK_SET);

	//  Allocate new space for the bmpImage
	bmpImage = new IMAGE;

	if(bmpImage == NULL)
	{
		//  Memory allocation failed so free the bmpImage, close the file, and return NULL
		delete bmpImage;
		fclose(file);

		return NULL;
	}

	//  Allocate enough memory for the bitmap image data
	bmpImage->data = new unsigned char[bitmapInfoHeader.biSizeImage];

	//  Verify memory allocation
	if(bmpImage->data == NULL)
	{
		//  Memory allocation failed so free the bitmapImage data, free the bmpImage, close the file, and return NULL
		delete [] bmpImage->data;
		delete bmpImage;
		fclose(file);

		return NULL;
	}

	//  Read in the bitmap image data
	fread(bmpImage->data, 1, bitmapInfoHeader.biSizeImage, file);

	//  Make sure the bitmap image data was read
	if(bmpImage->data == NULL)
	{
		//  Bitmap image was not read so free the bitmapImage data, free the bmpImage, close the file, and return NULL
		delete [] bmpImage->data;
		delete bmpImage;
		fclose(file);

		return NULL;
	}

	unsigned char tempRGB = NULL;	//  Temporary BGR->RGB swap variable

	//  Swap the R and B values to get RGB since the bitmap color format is in BGR
	for(int imageIdx = 0; imageIdx < bitmapInfoHeader.biSizeImage; imageIdx += 3)
	{
		tempRGB = bmpImage->data[imageIdx];
		bmpImage->data[imageIdx] = bmpImage->data[imageIdx + 2];
		bmpImage->data[imageIdx + 2] = tempRGB;
	}

	fclose(file);			//  Close the file

	return bmpImage;		//  Return the bitmap image since it was a success
}

//  Loads a Targa image format file
IMAGE* GLImage::LoadTGAFile(char *filename)
{
	//  Open the filename in "read binary" mode
	file = fopen(filename, "rb");

	//  If the file couldn''t be opened return NULL
	if(file == NULL)
		return NULL;

	//  Read first two bytes of data we don''t need
	fread(&ucharBad, sizeof(unsigned char), 1, file);
	fread(&ucharBad, sizeof(unsigned char), 1, file);

	//  Read in the image type
	fread(&imageTypeCode, sizeof(unsigned char), 1, file);

	//  Currently supported Targa file formats are 2-Uncompressed RGB and 3-Uncompressed black and white
	if(imageTypeCode != 2 && imageTypeCode != 3)
	{
		//  If it is not a supported type of Targa image close the file and return NULL
		fclose(file);

		return NULL;
	}

	//  Read 13 bytes of data we don''t need
	fread(&sintBad, sizeof(short int), 1, file);
	fread(&sintBad, sizeof(short int), 1, file);
	fread(&ucharBad, sizeof(unsigned char), 1, file);
	fread(&sintBad, sizeof(short int), 1, file);
	fread(&sintBad, sizeof(short int), 1, file);

	//  Allocate new space for the tgaImage
	tgaImage = new IMAGE;

	if(tgaImage == NULL)
	{
		//  Memory allocation failed so free the tgaImage, close the file, and return NULL
		delete tgaImage;
		fclose(file);

		return NULL;
	}

	//  Read image dimensions
	fread(&tgaImage->width, sizeof(short int), 1, file);
	fread(&tgaImage->height, sizeof(short int), 1, file);

	//  Read image bit depth
	fread(&bitCount, sizeof(unsigned char), 1, file);

	//  Read one byte of data we don''t need
	fread(&ucharBad, sizeof(unsigned char), 1, file);

	//  colorMode -> 3 = BGR, 4 = BGRA
	colorMode = bitCount / 8;
	imageSize = tgaImage->width * tgaImage->height * colorMode;

	//  Allocate memory for the image data
	tgaImage->data = new unsigned char[sizeof(unsigned char) * imageSize];

	//  Verify memory allocation
	if(tgaImage->data == NULL)
	{
		//  Memory allocation failed so free the targaImage data, free the tgaImage, close the file, and return NULL
		delete [] tgaImage->data;
		delete tgaImage;
		fclose(file);

		return NULL;
	}
	
	//  Read in the image data
	fread(tgaImage->data, sizeof(unsigned char), imageSize, file);

	//  Make sure the targa image data was read
	if(tgaImage->data == NULL)
	{
		//  Targa image was not read so free the targaImage data, free the tgaImage, close the file, and return NULL
		delete [] tgaImage->data;
		delete tgaImage;
		fclose(file);

		return NULL;
	}

	unsigned char colorSwap;	//  Swap variable used to exchange the R and B values

	//  Change BGR to RGB so OpenGL can read the image data
	for(int imageIdx = 0; imageIdx < imageSize; imageIdx += colorMode)
	{
		colorSwap = tgaImage->data[imageIdx];
		tgaImage->data[imageIdx] = tgaImage->data[imageIdx + 2];
		tgaImage->data[imageIdx + 2] = colorSwap;
	}

	fclose(file);		//  Close the file

	return tgaImage;	//  Loading of the TGA file was a successs
}
I think the way to use it in the code is self-explanatory if you have done this type of thing before. It goes a little like this: texture; IMAGE* image; GLImage i; // Load The Bitmap, Check For Errors, If Bitmap''s Not Found Quit if (TextureImage[0]=LoadBMP("Data/Crate.bmp")) { glGenTextures(1, &texture); glBindTexture(GL_TEXTURE_2D, texture); glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_NEAREST); glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_NEAREST); glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, image->width, image->height, 0, GL_RGB, GL_UNSIGNED_BYTE, image->data); } ..... Clear the memory ..... Etc. Ok, well if you have survived it this far ;-) I really appreciate that you took time out of your busy schedule to help me. If I was going to guess it is a pointer problem somewhere, but I can''t find it. I have also tried using the gluBuild2DMipmaps() in place of the glTexImage2D. I also get an error if the width is greater than 128. I tested it on three different comps with different video cards etc. and it still gave an error. SO, if you can help me in the smallest way my day will be a lot brighter. THANKS!

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#2 StiNKy   Members   -  Reputation: 144

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Posted 03 September 2001 - 06:48 PM

Thats a lot of weird lookin code...
All I can say is, the bitmap/targa file width and height both need to be a power of two, ie 16, 32, 64, etc. Also... I wrote my own bitmap and targa loading routines and I found that some types swapped the blue and red colours round, I think it was blue and red anyway... So don''t be discouraged if you see weird colours.

#3 mkaltner   Members   -  Reputation: 122

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Posted 06 September 2001 - 06:41 AM

I had a problem with loading bitmaps as well. Per the advice of someone else here, I tried saving my bitmaps with PaintShop Pro 7 and everything work perfectly after that. You can download it free (demo) from their site. Just do a google search for PaintShop Pro and you''ll find it.

- Mike




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