grf.cpp

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00001 /* $Id: grf.cpp 11940 2008-01-22 07:27:06Z peter1138 $ */
00002 
00005 #include "../stdafx.h"
00006 #include "../gfx_func.h"
00007 #include "../fileio.h"
00008 #include "../debug.h"
00009 #include "../core/alloc_func.hpp"
00010 #include "grf.hpp"
00011 
00012 bool SpriteLoaderGrf::LoadSprite(SpriteLoader::Sprite *sprite, uint8 file_slot, uint32 file_pos)
00013 {
00014   /* Open the right file and go to the correct position */
00015   FioSeekToFile(file_slot, file_pos);
00016 
00017   /* Read the size and type */
00018   int num = FioReadWord();
00019   byte type = FioReadByte();
00020 
00021   /* Type 0xFF indicates either a colormap or some other non-sprite info; we do not handle them here */
00022   if (type == 0xFF) return false;
00023 
00024   sprite->height = FioReadByte();
00025   sprite->width  = FioReadWord();
00026   sprite->x_offs = FioReadWord();
00027   sprite->y_offs = FioReadWord();
00028 
00029   /* 0x02 indicates it is a compressed sprite, so we can't rely on 'num' to be valid.
00030    *  In case it is uncompressed, the size is 'num' - 8 (header-size). */
00031   num = (type & 0x02) ? sprite->width * sprite->height : num - 8;
00032 
00033   /* XXX -- We should use a pre-located memory segment for this, malloc/free is pretty expensive */
00034   byte *dest_orig = MallocT<byte>(num);
00035   byte *dest = dest_orig;
00036 
00037   /* Read the file, which has some kind of compression */
00038   while (num > 0) {
00039     int8 code = FioReadByte();
00040 
00041     if (code >= 0) {
00042       /* Plain bytes to read */
00043       int size = (code == 0) ? 0x80 : code;
00044       num -= size;
00045       for (; size > 0; size--) {
00046         *dest = FioReadByte();
00047         dest++;
00048       }
00049     } else {
00050       /* Copy bytes from earlier in the sprite */
00051       const uint data_offset = ((code & 7) << 8) | FioReadByte();
00052       int size = -(code >> 3);
00053       num -= size;
00054       for (; size > 0; size--) {
00055         *dest = *(dest - data_offset);
00056         dest++;
00057       }
00058     }
00059   }
00060 
00061   assert(num == 0);
00062 
00063   sprite->data = CallocT<SpriteLoader::CommonPixel>(sprite->width * sprite->height);
00064 
00065   /* When there are transparency pixels, this format has an other trick.. decode it */
00066   if (type & 0x08) {
00067     for (int y = 0; y < sprite->height; y++) {
00068       bool last_item = false;
00069       /* Look up in the header-table where the real data is stored for this row */
00070       int offset = (dest_orig[y * 2 + 1] << 8) | dest_orig[y * 2];
00071       /* Go to that row */
00072       dest = &dest_orig[offset];
00073 
00074       do {
00075         SpriteLoader::CommonPixel *data;
00076         /* Read the header:
00077          *  0 .. 14  - length
00078          *  15       - last_item
00079          *  16 .. 31 - transparency bytes */
00080         last_item  = ((*dest) & 0x80) != 0;
00081         int length =  (*dest++) & 0x7F;
00082         int skip   =   *dest++;
00083 
00084         data = &sprite->data[y * sprite->width + skip];
00085 
00086         for (int x = 0; x < length; x++) {
00087           data->m = *dest;
00088           dest++;
00089           data++;
00090         }
00091       } while (!last_item);
00092     }
00093   } else {
00094     dest = dest_orig;
00095     for (int i = 0; i < sprite->width * sprite->height; i++)
00096       sprite->data[i].m = dest[i];
00097   }
00098 
00099   /* Make sure to mark all transparent pixels transparent on the alpha channel too */
00100   for (int i = 0; i < sprite->width * sprite->height; i++)
00101     if (sprite->data[i].m != 0) sprite->data[i].a = 0xFF;
00102 
00103   free(dest_orig);
00104   return true;
00105 }

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