# dlib C++ Library - rdtarga.c

    /*
     * rdtarga.c
     *
     * Copyright (C) 1991-1996, Thomas G. Lane.
     * This file is part of the Independent JPEG Group's software.
     * For conditions of distribution and use, see the accompanying README file.
     *
     * This file contains routines to read input images in Targa format.
     *
     * These routines may need modification for non-Unix environments or
     * specialized applications.  As they stand, they assume input from
     * an ordinary stdio stream.  They further assume that reading begins
     * at the start of the file; start_input may need work if the
     * user interface has already read some data (e.g., to determine that
     * the file is indeed Targa format).
     *
     * Based on code contributed by Lee Daniel Crocker.
     */

    #include "cdjpeg.h"		/* Common decls for cjpeg/djpeg applications */

    #ifdef TARGA_SUPPORTED

    /* Macros to deal with unsigned chars as efficiently as compiler allows */

    #ifdef HAVE_UNSIGNED_CHAR
    typedef unsigned char U_CHAR;
    #define UCH(x)	((int) (x))
    #else /* !HAVE_UNSIGNED_CHAR */
    #ifdef CHAR_IS_UNSIGNED
    typedef char U_CHAR;
    #define UCH(x)	((int) (x))
    #else
    typedef char U_CHAR;
    #define UCH(x)	((int) (x) & 0xFF)
    #endif
    #endif /* HAVE_UNSIGNED_CHAR */

    #define	ReadOK(file,buffer,len)	(JFREAD(file,buffer,len) == ((size_t) (len)))

    /* Private version of data source object */

    typedef struct _tga_source_struct * tga_source_ptr;

    typedef struct _tga_source_struct {
      struct cjpeg_source_struct pub; /* public fields */

      j_compress_ptr cinfo;		/* back link saves passing separate parm */

      JSAMPARRAY colormap;		/* Targa colormap (converted to my format) */

      jvirt_sarray_ptr whole_image;	/* Needed if funny input row order */
      JDIMENSION current_row;	/* Current logical row number to read */

      /* Pointer to routine to extract next Targa pixel from input file */
      JMETHOD(void, read_pixel, (tga_source_ptr sinfo));

      /* Result of read_pixel is delivered here: */
      U_CHAR tga_pixel[4];

      int pixel_size;		/* Bytes per Targa pixel (1 to 4) */

      /* State info for reading RLE-coded pixels; both counts must be init to 0 */
      int block_count;		/* # of pixels remaining in RLE block */
      int dup_pixel_count;		/* # of times to duplicate previous pixel */

      /* This saves the correct pixel-row-expansion method for preload_image */
      JMETHOD(JDIMENSION, get_pixel_rows, (j_compress_ptr cinfo,
    				       cjpeg_source_ptr sinfo));
    } tga_source_struct;

    /* For expanding 5-bit pixel values to 8-bit with best rounding */

    static const UINT8 c5to8bits[32] = {
        0,   8,  16,  25,  33,  41,  49,  58,
       66,  74,  82,  90,  99, 107, 115, 123,
      132, 140, 148, 156, 165, 173, 181, 189,
      197, 206, 214, 222, 230, 239, 247, 255
    };

    LOCAL(int)
    read_byte (tga_source_ptr sinfo)
    /* Read next byte from Targa file */
    {
      register FILE *infile = sinfo->pub.input_file;
      register int c;

      if ((c = getc(infile)) == EOF)
        ERREXIT(sinfo->cinfo, JERR_INPUT_EOF);
      return c;
    }

    LOCAL(void)
    read_colormap (tga_source_ptr sinfo, int cmaplen, int mapentrysize)
    /* Read the colormap from a Targa file */
    {
      int i;

      /* Presently only handles 24-bit BGR format */
      if (mapentrysize != 24)
        ERREXIT(sinfo->cinfo, JERR_TGA_BADCMAP);

      for (i = 0; i < cmaplen; i++) {
        sinfo->colormap[2][i] = (JSAMPLE) read_byte(sinfo);
        sinfo->colormap[1][i] = (JSAMPLE) read_byte(sinfo);
        sinfo->colormap[0][i] = (JSAMPLE) read_byte(sinfo);
      }
    }

    /*
     * read_pixel methods: get a single pixel from Targa file into tga_pixel[]
     */

    METHODDEF(void)
    read_non_rle_pixel (tga_source_ptr sinfo)
    /* Read one Targa pixel from the input file; no RLE expansion */
    {
      register FILE *infile = sinfo->pub.input_file;
      register int i;

      for (i = 0; i < sinfo->pixel_size; i++) {
        sinfo->tga_pixel[i] = (U_CHAR) getc(infile);
      }
    }

    METHODDEF(void)
    read_rle_pixel (tga_source_ptr sinfo)
    /* Read one Targa pixel from the input file, expanding RLE data as needed */
    {
      register FILE *infile = sinfo->pub.input_file;
      register int i;

      /* Duplicate previously read pixel? */
      if (sinfo->dup_pixel_count > 0) {
        sinfo->dup_pixel_count--;
        return;
      }

      /* Time to read RLE block header? */
      if (--sinfo->block_count < 0) { /* decrement pixels remaining in block */
        i = read_byte(sinfo);
        if (i & 0x80) {		/* Start of duplicate-pixel block? */
          sinfo->dup_pixel_count = i & 0x7F; /* number of dups after this one */
          sinfo->block_count = 0;	/* then read new block header */
        } else {
          sinfo->block_count = i & 0x7F; /* number of pixels after this one */
        }
      }

      /* Read next pixel */
      for (i = 0; i < sinfo->pixel_size; i++) {
        sinfo->tga_pixel[i] = (U_CHAR) getc(infile);
      }
    }

    /*
     * Read one row of pixels.
     *
     * We provide several different versions depending on input file format.
     */

    METHODDEF(JDIMENSION)
    get_8bit_gray_row (j_compress_ptr cinfo, cjpeg_source_ptr sinfo)
    /* This version is for reading 8-bit grayscale pixels */
    {
      tga_source_ptr source = (tga_source_ptr) sinfo;
      register JSAMPROW ptr;
      register JDIMENSION col;

      ptr = source->pub.buffer[0];
      for (col = cinfo->image_width; col > 0; col--) {
        (*source->read_pixel) (source); /* Load next pixel into tga_pixel */
        *ptr++ = (JSAMPLE) UCH(source->tga_pixel[0]);
      }
      return 1;
    }

    METHODDEF(JDIMENSION)
    get_8bit_row (j_compress_ptr cinfo, cjpeg_source_ptr sinfo)
    /* This version is for reading 8-bit colormap indexes */
    {
      tga_source_ptr source = (tga_source_ptr) sinfo;
      register int t;
      register JSAMPROW ptr;
      register JDIMENSION col;
      register JSAMPARRAY colormap = source->colormap;

      ptr = source->pub.buffer[0];
      for (col = cinfo->image_width; col > 0; col--) {
        (*source->read_pixel) (source); /* Load next pixel into tga_pixel */
        t = UCH(source->tga_pixel[0]);
        *ptr++ = colormap[0][t];
        *ptr++ = colormap[1][t];
        *ptr++ = colormap[2][t];
      }
      return 1;
    }

    METHODDEF(JDIMENSION)
    get_16bit_row (j_compress_ptr cinfo, cjpeg_source_ptr sinfo)
    /* This version is for reading 16-bit pixels */
    {
      tga_source_ptr source = (tga_source_ptr) sinfo;
      register int t;
      register JSAMPROW ptr;
      register JDIMENSION col;

      ptr = source->pub.buffer[0];
      for (col = cinfo->image_width; col > 0; col--) {
        (*source->read_pixel) (source); /* Load next pixel into tga_pixel */
        t = UCH(source->tga_pixel[0]);
        t += UCH(source->tga_pixel[1]) << 8;
        /* We expand 5 bit data to 8 bit sample width.
         * The format of the 16-bit (LSB first) input word is
         *     xRRRRRGGGGGBBBBB
         */
        ptr[2] = (JSAMPLE) c5to8bits[t & 0x1F];
        t >>= 5;
        ptr[1] = (JSAMPLE) c5to8bits[t & 0x1F];
        t >>= 5;
        ptr[0] = (JSAMPLE) c5to8bits[t & 0x1F];
        ptr += 3;
      }
      return 1;
    }

    METHODDEF(JDIMENSION)
    get_24bit_row (j_compress_ptr cinfo, cjpeg_source_ptr sinfo)
    /* This version is for reading 24-bit pixels */
    {
      tga_source_ptr source = (tga_source_ptr) sinfo;
      register JSAMPROW ptr;
      register JDIMENSION col;

      ptr = source->pub.buffer[0];
      for (col = cinfo->image_width; col > 0; col--) {
        (*source->read_pixel) (source); /* Load next pixel into tga_pixel */
        *ptr++ = (JSAMPLE) UCH(source->tga_pixel[2]); /* change BGR to RGB order */
        *ptr++ = (JSAMPLE) UCH(source->tga_pixel[1]);
        *ptr++ = (JSAMPLE) UCH(source->tga_pixel[0]);
      }
      return 1;
    }

    /*
     * Targa also defines a 32-bit pixel format with order B,G,R,A.
     * We presently ignore the attribute byte, so the code for reading
     * these pixels is identical to the 24-bit routine above.
     * This works because the actual pixel length is only known to read_pixel.
     */

    #define get_32bit_row  get_24bit_row

    /*
     * This method is for re-reading the input data in standard top-down
     * row order.  The entire image has already been read into whole_image
     * with proper conversion of pixel format, but it's in a funny row order.
     */

    METHODDEF(JDIMENSION)
    get_memory_row (j_compress_ptr cinfo, cjpeg_source_ptr sinfo)
    {
      tga_source_ptr source = (tga_source_ptr) sinfo;
      JDIMENSION source_row;

      /* Compute row of source that maps to current_row of normal order */
      /* For now, assume image is bottom-up and not interlaced. */
      /* NEEDS WORK to support interlaced images! */
      source_row = cinfo->image_height - source->current_row - 1;

      /* Fetch that row from virtual array */
      source->pub.buffer = (*cinfo->mem->access_virt_sarray)
        ((j_common_ptr) cinfo, source->whole_image,
         source_row, (JDIMENSION) 1, FALSE);

      source->current_row++;
      return 1;
    }

    /*
     * This method loads the image into whole_image during the first call on
     * get_pixel_rows.  The get_pixel_rows pointer is then adjusted to call
     * get_memory_row on subsequent calls.
     */

    METHODDEF(JDIMENSION)
    preload_image (j_compress_ptr cinfo, cjpeg_source_ptr sinfo)
    {
      tga_source_ptr source = (tga_source_ptr) sinfo;
      JDIMENSION row;
      cd_progress_ptr progress = (cd_progress_ptr) cinfo->progress;

      /* Read the data into a virtual array in input-file row order. */
      for (row = 0; row < cinfo->image_height; row++) {
        if (progress != NULL) {
          progress->pub.pass_counter = (long) row;
          progress->pub.pass_limit = (long) cinfo->image_height;
          (*progress->pub.progress_monitor) ((j_common_ptr) cinfo);
        }
        source->pub.buffer = (*cinfo->mem->access_virt_sarray)
          ((j_common_ptr) cinfo, source->whole_image, row, (JDIMENSION) 1, TRUE);
        (*source->get_pixel_rows) (cinfo, sinfo);
      }
      if (progress != NULL)
        progress->completed_extra_passes++;

      /* Set up to read from the virtual array in unscrambled order */
      source->pub.get_pixel_rows = get_memory_row;
      source->current_row = 0;
      /* And read the first row */
      return get_memory_row(cinfo, sinfo);
    }

    /*
     * Read the file header; return image size and component count.
     */

    METHODDEF(void)
    start_input_tga (j_compress_ptr cinfo, cjpeg_source_ptr sinfo)
    {
      tga_source_ptr source = (tga_source_ptr) sinfo;
      U_CHAR targaheader[18];
      int idlen, cmaptype, subtype, flags, interlace_type, components;
      unsigned int width, height, maplen;
      boolean is_bottom_up;

    #define GET_2B(offset)	((unsigned int) UCH(targaheader[offset]) + \
    			 (((unsigned int) UCH(targaheader[offset+1])) << 8))

      if (! ReadOK(source->pub.input_file, targaheader, 18))
        ERREXIT(cinfo, JERR_INPUT_EOF);

      /* Pretend "15-bit" pixels are 16-bit --- we ignore attribute bit anyway */
      if (targaheader[16] == 15)
        targaheader[16] = 16;

      idlen = UCH(targaheader[0]);
      cmaptype = UCH(targaheader[1]);
      subtype = UCH(targaheader[2]);
      maplen = GET_2B(5);
      width = GET_2B(12);
      height = GET_2B(14);
      source->pixel_size = UCH(targaheader[16]) >> 3;
      flags = UCH(targaheader[17]);	/* Image Descriptor byte */

      is_bottom_up = ((flags & 0x20) == 0);	/* bit 5 set => top-down */
      interlace_type = flags >> 6;	/* bits 6/7 are interlace code */

      if (cmaptype > 1 ||		/* cmaptype must be 0 or 1 */
          source->pixel_size < 1 || source->pixel_size > 4 ||
          (UCH(targaheader[16]) & 7) != 0 || /* bits/pixel must be multiple of 8 */
          interlace_type != 0)	/* currently don't allow interlaced image */
        ERREXIT(cinfo, JERR_TGA_BADPARMS);

      if (subtype > 8) {
        /* It's an RLE-coded file */
        source->read_pixel = read_rle_pixel;
        source->block_count = source->dup_pixel_count = 0;
        subtype -= 8;
      } else {
        /* Non-RLE file */
        source->read_pixel = read_non_rle_pixel;
      }

      /* Now should have subtype 1, 2, or 3 */
      components = 3;		/* until proven different */
      cinfo->in_color_space = JCS_RGB;

      switch (subtype) {
      case 1:			/* Colormapped image */
        if (source->pixel_size == 1 && cmaptype == 1)
          source->get_pixel_rows = get_8bit_row;
        else
          ERREXIT(cinfo, JERR_TGA_BADPARMS);
        TRACEMS2(cinfo, 1, JTRC_TGA_MAPPED, width, height);
        break;
      case 2:			/* RGB image */
        switch (source->pixel_size) {
        case 2:
          source->get_pixel_rows = get_16bit_row;
          break;
        case 3:
          source->get_pixel_rows = get_24bit_row;
          break;
        case 4:
          source->get_pixel_rows = get_32bit_row;
          break;
        default:
          ERREXIT(cinfo, JERR_TGA_BADPARMS);
          break;
        }
        TRACEMS2(cinfo, 1, JTRC_TGA, width, height);
        break;
      case 3:			/* Grayscale image */
        components = 1;
        cinfo->in_color_space = JCS_GRAYSCALE;
        if (source->pixel_size == 1)
          source->get_pixel_rows = get_8bit_gray_row;
        else
          ERREXIT(cinfo, JERR_TGA_BADPARMS);
        TRACEMS2(cinfo, 1, JTRC_TGA_GRAY, width, height);
        break;
      default:
        ERREXIT(cinfo, JERR_TGA_BADPARMS);
        break;
      }

      if (is_bottom_up) {
        /* Create a virtual array to buffer the upside-down image. */
        source->whole_image = (*cinfo->mem->request_virt_sarray)
          ((j_common_ptr) cinfo, JPOOL_IMAGE, FALSE,
           (JDIMENSION) width * components, (JDIMENSION) height, (JDIMENSION) 1);
        if (cinfo->progress != NULL) {
          cd_progress_ptr progress = (cd_progress_ptr) cinfo->progress;
          progress->total_extra_passes++; /* count file input as separate pass */
        }
        /* source->pub.buffer will point to the virtual array. */
        source->pub.buffer_height = 1; /* in case anyone looks at it */
        source->pub.get_pixel_rows = preload_image;
      } else {
        /* Don't need a virtual array, but do need a one-row input buffer. */
        source->whole_image = NULL;
        source->pub.buffer = (*cinfo->mem->alloc_sarray)
          ((j_common_ptr) cinfo, JPOOL_IMAGE,
           (JDIMENSION) width * components, (JDIMENSION) 1);
        source->pub.buffer_height = 1;
        source->pub.get_pixel_rows = source->get_pixel_rows;
      }

      while (idlen--)		/* Throw away ID field */
        (void) read_byte(source);

      if (maplen > 0) {
        if (maplen > 256 || GET_2B(3) != 0)
          ERREXIT(cinfo, JERR_TGA_BADCMAP);
        /* Allocate space to store the colormap */
        source->colormap = (*cinfo->mem->alloc_sarray)
          ((j_common_ptr) cinfo, JPOOL_IMAGE, (JDIMENSION) maplen, (JDIMENSION) 3);
        /* and read it from the file */
        read_colormap(source, (int) maplen, UCH(targaheader[7]));
      } else {
        if (cmaptype)		/* but you promised a cmap! */
          ERREXIT(cinfo, JERR_TGA_BADPARMS);
        source->colormap = NULL;
      }

      cinfo->input_components = components;
      cinfo->data_precision = 8;
      cinfo->image_width = width;
      cinfo->image_height = height;
    }

    /*
     * Finish up at the end of the file.
     */

    METHODDEF(void)
    finish_input_tga (j_compress_ptr cinfo, cjpeg_source_ptr sinfo)
    {
      /* no work */
    }

    /*
     * The module selection routine for Targa format input.
     */

    GLOBAL(cjpeg_source_ptr)
    jinit_read_targa (j_compress_ptr cinfo)
    {
      tga_source_ptr source;

      /* Create module interface object */
      source = (tga_source_ptr)
          (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
    				  SIZEOF(tga_source_struct));
      source->cinfo = cinfo;	/* make back link for subroutines */
      /* Fill in method ptrs, except get_pixel_rows which start_input sets */
      source->pub.start_input = start_input_tga;
      source->pub.finish_input = finish_input_tga;

      return (cjpeg_source_ptr) source;
    }

    #endif /* TARGA_SUPPORTED */