forked from 0ad/0ad
janwas
f4c535a326
self_test: add dox (also to wiki) tex_codecs: further work; renamed+reorg for clarity. separating codecs from IO implementation This was SVN commit r2654.
143 lines
3.2 KiB
C++
143 lines
3.2 KiB
C++
#include "precompiled.h"
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#include "lib/byte_order.h"
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#include "tex_codec.h"
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#pragma pack(push, 1)
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struct BmpHeader
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{
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// BITMAPFILEHEADER
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u16 bfType; // "BM"
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u32 bfSize; // of file
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u16 bfReserved1;
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u16 bfReserved2;
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u32 bfOffBits; // offset to image data
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// BITMAPINFOHEADER
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u32 biSize;
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long biWidth;
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long biHeight;
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u16 biPlanes;
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u16 biBitCount;
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u32 biCompression;
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u32 biSizeImage;
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// the following are unused and zeroed when writing:
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long biXPelsPerMeter;
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long biYPelsPerMeter;
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u32 biClrUsed;
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u32 biClrImportant;
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};
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#pragma pack(pop)
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#define BI_RGB 0 // biCompression
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static int bmp_transform(Tex* t, int new_flags)
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{
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return TEX_CODEC_CANNOT_HANDLE;
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}
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// requirements: uncompressed, direct colour, bottom up
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static int bmp_decode(u8* file, size_t file_size, Tex* t, const char** perr_msg)
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{
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// check header signature (bfType == "BM"?).
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// we compare single bytes to be endian-safe.
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if(file[0] != 'B' || file[1] != 'M')
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return TEX_CODEC_CANNOT_HANDLE;
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const size_t hdr_size = sizeof(BmpHeader);
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// make sure we can access all header fields
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if(file_size < hdr_size)
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{
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*perr_msg = "header not completely read";
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fail:
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return ERR_CORRUPTED;
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}
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const BmpHeader* hdr = (const BmpHeader*)file;
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const long w = (long)read_le32(&hdr->biWidth);
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const long h_ = (long)read_le32(&hdr->biHeight);
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const u16 bpp = read_le16(&hdr->biBitCount);
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const u32 compress = read_le32(&hdr->biCompression);
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const u32 ofs = read_le32(&hdr->bfOffBits);
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const int orientation = (h_ < 0)? TEX_TOP_DOWN : TEX_BOTTOM_UP;
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const long h = abs(h_);
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const size_t pitch = w * bpp/8;
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const size_t img_size = h * pitch;
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u8* const img = file + ofs;
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int flags = TEX_BGR;
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if(bpp == 32)
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flags |= TEX_ALPHA;
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// sanity checks
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const char* err = 0;
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if(compress != BI_RGB)
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err = "compressed";
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if(bpp != 24 && bpp != 32)
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err = "invalid bpp (not direct colour)";
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if(file_size < ofs+img_size)
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err = "image not completely read";
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if(err)
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{
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*perr_msg = err;
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goto fail;
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}
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t->ofs = ofs;
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t->w = w;
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t->h = h;
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t->bpp = bpp;
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t->flags = flags;
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tex_codec_set_orientation(t, orientation);
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return 0;
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}
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static int bmp_encode(const char* ext, Tex* t, u8** out, size_t* out_size, const char** perr_msg)
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{
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if(stricmp(ext, "bmp"))
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return TEX_CODEC_CANNOT_HANDLE;
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size_t img_size = t->w * t->h * t->bpp/8;
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const size_t hdr_size = sizeof(BmpHeader); // needed for BITMAPFILEHEADER
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const size_t file_size = hdr_size + img_size;
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const long h = (t->flags & TEX_TOP_DOWN)? -(long)t->h : t->h;
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int transforms = t->flags;
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transforms &= ~TEX_ORIENTATION; // no flip needed - we can set top-down bit.
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transforms ^= TEX_BGR; // BMP is native BGR.
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tex_transform(t, transforms);
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const BmpHeader hdr =
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{
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// BITMAPFILEHEADER
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0x4d42, // bfType = 'B','M'
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(u32)file_size, // bfSize
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0, 0, // bfReserved1,2
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hdr_size, // bfOffBits
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// BITMAPINFOHEADER
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40, // biSize = sizeof(BITMAPINFOHEADER)
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t->w,
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h,
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1, // biPlanes
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t->bpp,
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BI_RGB, // biCompression
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(u32)img_size, // biSizeImage
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0, 0, 0, 0 // unused (bi?PelsPerMeter, biClr*)
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};
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return 0;
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}
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TEX_CODEC_REGISTER(bmp);
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