readtex.c

嵌入式GUI OpenGL源代码。OpenGL是嵌入式开发中常用的一种GUI系统。

/* readtex.c */

/* 
 * Read an SGI .rgb image file and generate a mipmap texture set.
 * Much of this code was borrowed from SGI's tk OpenGL toolkit.
 */

#include <GL/glut.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "readtex.h"

#ifndef SEEK_SET
#define SEEK_SET 0
#endif

/* RGB Image Structure */

typedef struct _TK_RGBImageRec {
  GLint sizeX, sizeY;
  GLint components;
  unsigned char *data;
} TK_RGBImageRec;

/******************************************************************************/

typedef struct _rawImageRec {
  unsigned short imagic;
  unsigned short type;
  unsigned short dim;
  unsigned short sizeX, sizeY, sizeZ;
  unsigned long min, max;
  unsigned long wasteBytes;
  char name[80];
  unsigned long colorMap;
  FILE *file;
  unsigned char *tmp, *tmpR, *tmpG, *tmpB, *tmpA;
  unsigned long rleEnd;
  GLuint *rowStart;
  GLint *rowSize;
} rawImageRec;

/******************************************************************************/

static void 
ConvertShort(unsigned short *array, size_t length)
{
  unsigned short b1, b2;
  unsigned char *ptr;

  ptr = (unsigned char *) array;
  while (length--) {
    b1 = *ptr++;
    b2 = *ptr++;
    *array++ = (b1 << 8) | (b2);
  }
}

static void 
ConvertLong(GLuint * array, size_t length)
{
  unsigned long b1, b2, b3, b4;
  unsigned char *ptr;

  ptr = (unsigned char *) array;
  while (length--) {
    b1 = *ptr++;
    b2 = *ptr++;
    b3 = *ptr++;
    b4 = *ptr++;
    *array++ = (b1 << 24) | (b2 << 16) | (b3 << 8) | (b4);
  }
}

static rawImageRec *
RawImageOpen(const char *fileName)
{
  union {
    int testWord;
    char testByte[4];
  } endianTest;
  rawImageRec *raw;
  GLenum swapFlag;
  int x;

  endianTest.testWord = 1;
  if (endianTest.testByte[0] == 1) {
    swapFlag = GL_TRUE;
  } else {
    swapFlag = GL_FALSE;
  }

  raw = (rawImageRec *) malloc(sizeof(rawImageRec));
  if (raw == NULL) {
    fprintf(stderr, "Out of memory!\n");
    return NULL;
  }
  if ((raw->file = fopen(fileName, "rb")) == NULL) {
    perror(fileName);
    return NULL;
  }
  fread(raw, 1, 12, raw->file);

  if (swapFlag) {
    ConvertShort(&raw->imagic, 6);
  }
  raw->tmp = (unsigned char *) malloc(raw->sizeX * 256);
  if (raw->tmp == NULL) {
    fprintf(stderr, "Out of memory!\n");
    return NULL;
  }
  raw->tmpR = (unsigned char *) malloc(raw->sizeX * 256);
  if (raw->tmpR == NULL) {
    fprintf(stderr, "Out of memory!\n");
    return NULL;
  }
  if (raw->sizeZ > 1) {
    raw->tmpG = (unsigned char *) malloc(raw->sizeX * 256);
    raw->tmpB = (unsigned char *) malloc(raw->sizeX * 256);
    if (raw->tmpG == NULL || raw->tmpB == NULL) {
      fprintf(stderr, "Out of memory!\n");
      return NULL;
    }
    if (raw->sizeZ == 4) {
      raw->tmpA = (unsigned char *) malloc(raw->sizeX * 256);
      if (raw->tmpA == NULL) {
        fprintf(stderr, "Out of memory!\n");
        return NULL;
      }
    }
  }
  if ((raw->type & 0xFF00) == 0x0100) {
    x = raw->sizeY * raw->sizeZ * sizeof(GLuint);
    raw->rowStart = (GLuint *) malloc(x);
    raw->rowSize = (GLint *) malloc(x);
    if (raw->rowStart == NULL || raw->rowSize == NULL) {
      fprintf(stderr, "Out of memory!\n");
      return NULL;
    }
    raw->rleEnd = 512 + (2 * x);
    fseek(raw->file, 512, SEEK_SET);
    fread(raw->rowStart, 1, x, raw->file);
    fread(raw->rowSize, 1, x, raw->file);
    if (swapFlag) {
      ConvertLong(raw->rowStart, x / sizeof(GLuint));
      ConvertLong((GLuint *) raw->rowSize, x / sizeof(GLint));
    }
  }
  return raw;
}

static void 
RawImageClose(rawImageRec * raw)
{

  fclose(raw->file);
  free(raw->tmp);
  free(raw->tmpR);
  free(raw->tmpG);
  free(raw->tmpB);
  if (raw->sizeZ > 3) {
    free(raw->tmpA);
  }
  free(raw);
}

static void 
RawImageGetRow(rawImageRec * raw, unsigned char *buf, int y, int z)
{
  unsigned char *iPtr, *oPtr, pixel;
  int count;

  if ((raw->type & 0xFF00) == 0x0100) {
    fseek(raw->file, (long) raw->rowStart[y + z * raw->sizeY], SEEK_SET);
    fread(raw->tmp, 1, (size_t) raw->rowSize[y + z * raw->sizeY],
      raw->file);

    iPtr = raw->tmp;
    oPtr = buf;
    for (;;) {
      pixel = *iPtr++;
      count = (int) (pixel & 0x7F);
      if (!count) {
        return;
      }
      if (pixel & 0x80) {
        while (count--) {
          *oPtr++ = *iPtr++;
        }
      } else {
        pixel = *iPtr++;
        while (count--) {
          *oPtr++ = pixel;
        }
      }
    }
  } else {
    fseek(raw->file, 512 + (y * raw->sizeX) + (z * raw->sizeX * raw->sizeY),
      SEEK_SET);
    fread(buf, 1, raw->sizeX, raw->file);
  }
}

static void 
RawImageGetData(rawImageRec * raw, TK_RGBImageRec * final)
{
  unsigned char *ptr;
  int i, j;

  final->data = (unsigned char *) malloc((raw->sizeX + 1) * (raw->sizeY + 1) * 4);
  if (final->data == NULL) {
    fprintf(stderr, "Out of memory!\n");
  }
  ptr = final->data;
  for (i = 0; i < (int) (raw->sizeY); i++) {
    RawImageGetRow(raw, raw->tmpR, i, 0);
    if (raw->sizeZ > 1) {
      RawImageGetRow(raw, raw->tmpG, i, 1);
      RawImageGetRow(raw, raw->tmpB, i, 2);
      if (raw->sizeZ > 3) {
        RawImageGetRow(raw, raw->tmpA, i, 3);
      }
    }
    for (j = 0; j < (int) (raw->sizeX); j++) {
      *ptr++ = *(raw->tmpR + j);
      if (raw->sizeZ > 1) {
        *ptr++ = *(raw->tmpG + j);
        *ptr++ = *(raw->tmpB + j);
        if (raw->sizeZ > 3) {
          *ptr++ = *(raw->tmpA + j);
        }
      }
    }
  }
}

static TK_RGBImageRec *
tkRGBImageLoad(const char *fileName)
{
  rawImageRec *raw;
  TK_RGBImageRec *final;

  raw = RawImageOpen(fileName);
  final = (TK_RGBImageRec *) malloc(sizeof(TK_RGBImageRec));
  if (final == NULL) {
    fprintf(stderr, "Out of memory!\n");
    return NULL;
  }
  final->sizeX = raw->sizeX;
  final->sizeY = raw->sizeY;
  final->components = raw->sizeZ;
  RawImageGetData(raw, final);
  RawImageClose(raw);
  return final;
}

static void 
FreeImage(TK_RGBImageRec * image)
{
  free(image->data);
  free(image);
}

/* 
 * Load an SGI .rgb file and generate a set of 2-D mipmaps from it.
 * Input:  imageFile - name of .rgb to read
 *         intFormat - internal texture format to use, or number of components
 * Return:  GL_TRUE if success, GL_FALSE if error.
 */
GLboolean 
LoadRGBMipmaps(const char *imageFile, GLint intFormat)
{
  GLint error;
  GLenum format;
  TK_RGBImageRec *image;

  image = tkRGBImageLoad(imageFile);
  if (!image) {
    return GL_FALSE;
  }
  if (image->components == 3) {
    format = GL_RGB;
  } else if (image->components == 4) {
    format = GL_RGBA;
  } else if (image->components == 1) {
    format = GL_LUMINANCE;
    intFormat = 1;
  } else {
    /* not implemented */
    fprintf(stderr,
      "Error in LoadRGBMipmaps %d-component images not implemented\n",
      image->components);
    return GL_FALSE;
  }

  error = gluBuild2DMipmaps(GL_TEXTURE_2D,
    intFormat,
    image->sizeX, image->sizeY,
    format,
    GL_UNSIGNED_BYTE,
    image->data);

  FreeImage(image);
  return error ? GL_FALSE : GL_TRUE;
}