541 lines
21 KiB
C
541 lines
21 KiB
C
/*
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BMP File Reader/Writer Implementation
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Anton Gerdelan
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Version: 3
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Licence: see apg_bmp.h
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C99
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*/
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#ifdef _MSC_VER
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#define _CRT_SECURE_NO_WARNINGS 1
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#endif
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#include "apg_bmp.h"
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#include <assert.h>
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#include <stdbool.h>
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#include <stdint.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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/* Maximum pixel dimensions of width or height of an image. Should accommodate max used in graphics APIs.
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NOTE: 65536*65536 is the biggest number storable in 32 bits.
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This needs to be multiplied by n_channels so actual memory indices are not uint32 but size_t to avoid overflow.
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Note this will crash stb_image_write et al at maximum size which use 32bits, so reduce max size to accom. */
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#define _BMP_MAX_DIMS 65536
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#define _BMP_FILE_HDR_SZ 14
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#define _BMP_MIN_DIB_HDR_SZ 40
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#define _BMP_MIN_HDR_SZ ( _BMP_FILE_HDR_SZ + _BMP_MIN_DIB_HDR_SZ )
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#define _BMP_MAX_IMAGE_FILE_SIZE (1024ULL*1024ULL*1024ULL)
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#pragma pack( push, 1 ) // supported on GCC in addition to individual packing attribs
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/* All BMP files, regardless of type, start with this file header */
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typedef struct _bmp_file_header_t {
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char file_type[2];
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uint32_t file_sz;
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uint16_t reserved1;
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uint16_t reserved2;
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uint32_t image_data_offset;
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} _bmp_file_header_t;
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/* Following the file header is the BMP type header. this is the most commonly used format */
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typedef struct _bmp_dib_BITMAPINFOHEADER_t {
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uint32_t this_header_sz;
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int32_t w; // in older headers w & h these are shorts and may be unsigned
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int32_t h; //
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uint16_t n_planes; // must be 1
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uint16_t bpp; // bits per pixel. 1,4,8,16,24,32.
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uint32_t compression_method; // 16 and 32-bit images must have a value of 3 here
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uint32_t image_uncompressed_sz; // not consistently used in the wild, so ignored here.
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int32_t horiz_pixels_per_meter; // not used.
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int32_t vert_pixels_per_meter; // not used.
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uint32_t n_colours_in_palette; //
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uint32_t n_important_colours; // not used.
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/* NOTE(Anton) a DIB header may end here at 40-bytes. be careful using sizeof() */
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/* if 'compression' value, above, is set to 3 ie the image is 16 or 32-bit, then these colour channel masks follow the headers.
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these are big-endian order bit masks to assign bits of each pixel to different colours. bits used must be contiguous and not overlap. */
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uint32_t bitmask_r;
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uint32_t bitmask_g;
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uint32_t bitmask_b;
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} _bmp_dib_BITMAPINFOHEADER_t;
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#pragma pack( pop )
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typedef enum _bmp_compression_t {
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BI_RGB = 0,
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BI_RLE8 = 1,
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BI_RLE4 = 2,
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BI_BITFIELDS = 3,
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BI_JPEG = 4,
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BI_PNG = 5,
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BI_ALPHABITFIELDS = 6,
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BI_CMYK = 11,
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BI_CMYKRLE8 = 12,
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BI_CMYRLE4 = 13
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} _bmp_compression_t;
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/* convenience struct and file->memory function */
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typedef struct _entire_file_t {
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void* data;
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size_t sz;
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} _entire_file_t;
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/*
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RETURNS
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- true on success. record->data is allocated memory and must be freed by the caller.
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- false on any error. Any allocated memory is freed if false is returned */
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static bool _read_entire_file( const char* filename, _entire_file_t* record ) {
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FILE* fp = fopen( filename, "rb" );
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if ( !fp ) { return false; }
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fseek( fp, 0L, SEEK_END );
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record->sz = (size_t)ftell( fp );
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// Immediately bail on anything larger than _BMP_MAX_IMAGE_FILE_SIZE.
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if (record->sz > _BMP_MAX_IMAGE_FILE_SIZE) {
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fclose( fp );
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return false;
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}
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record->data = malloc( record->sz );
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if ( !record->data ) {
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fclose( fp );
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return false;
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}
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rewind( fp );
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size_t nr = fread( record->data, record->sz, 1, fp );
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fclose( fp );
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if ( 1 != nr ) { return false; }
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return true;
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}
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static bool _validate_file_hdr( _bmp_file_header_t* file_hdr_ptr, size_t file_sz ) {
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if ( !file_hdr_ptr ) { return false; }
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if ( file_hdr_ptr->file_type[0] != 'B' || file_hdr_ptr->file_type[1] != 'M' ) { return false; }
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if ( file_hdr_ptr->image_data_offset > file_sz ) { return false; }
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return true;
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}
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static bool _validate_dib_hdr( _bmp_dib_BITMAPINFOHEADER_t* dib_hdr_ptr, size_t file_sz ) {
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if ( !dib_hdr_ptr ) { return false; }
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if ( _BMP_FILE_HDR_SZ + dib_hdr_ptr->this_header_sz > file_sz ) { return false; }
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if ( ( 32 == dib_hdr_ptr->bpp || 16 == dib_hdr_ptr->bpp ) && ( BI_BITFIELDS != dib_hdr_ptr->compression_method && BI_ALPHABITFIELDS != dib_hdr_ptr->compression_method ) ) {
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return false;
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}
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if ( BI_RGB != dib_hdr_ptr->compression_method && BI_BITFIELDS != dib_hdr_ptr->compression_method && BI_ALPHABITFIELDS != dib_hdr_ptr->compression_method ) {
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return false;
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}
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// NOTE(Anton) using abs() in the if-statement was blowing up on large negative numbers. switched to labs()
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if ( 0 == dib_hdr_ptr->w || 0 == dib_hdr_ptr->h || labs( dib_hdr_ptr->w ) > _BMP_MAX_DIMS || labs( dib_hdr_ptr->h ) > _BMP_MAX_DIMS ) { return false; }
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/* NOTE(Anton) if images reliably used n_colours_in_palette we could have done a palette/file size integrity check here.
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because some always set 0 then we have to check every palette indexing as we read them */
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return true;
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}
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/* NOTE(Anton) this could have ifdef branches on different compilers for the intrinsics versions for perf */
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static uint32_t _bitscan( uint32_t dword ) {
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for ( uint32_t i = 0; i < 32; i++ ) {
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if ( 1 & dword ) { return i; }
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dword = dword >> 1;
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}
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return (uint32_t)-1;
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}
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unsigned char* apg_bmp_read( const char* filename, int* w, int* h, unsigned int* n_chans ) {
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if ( !filename || !w || !h || !n_chans ) { return NULL; }
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// read in the whole file into memory first - much faster than parsing on-the-fly
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_entire_file_t record;
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if ( !_read_entire_file( filename, &record ) ) { return NULL; }
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if ( record.sz < _BMP_MIN_HDR_SZ ) {
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free( record.data );
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return NULL;
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}
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// grab and validate the first, file, header
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_bmp_file_header_t* file_hdr_ptr = (_bmp_file_header_t*)record.data;
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if ( !_validate_file_hdr( file_hdr_ptr, record.sz ) ) {
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free( record.data );
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return NULL;
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}
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// grad and validate the second, DIB, header
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_bmp_dib_BITMAPINFOHEADER_t* dib_hdr_ptr = (_bmp_dib_BITMAPINFOHEADER_t*)( (uint8_t*)record.data + _BMP_FILE_HDR_SZ );
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if ( !_validate_dib_hdr( dib_hdr_ptr, record.sz ) ) {
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free( record.data );
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return NULL;
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}
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// bitmaps can have negative dims to indicate the image should be flipped
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uint32_t width = *w = abs( dib_hdr_ptr->w );
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uint32_t height = *h = abs( dib_hdr_ptr->h );
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// TODO(Anton) flip image memory at the end if this is true. because doing it per row was making me write bugs.
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// bool vertically_flip = dib_hdr_ptr->h > 0 ? false : true;
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// channel count and palette are not well defined in the header so we make a good guess here
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uint32_t n_dst_chans = 3, n_src_chans = 3;
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bool has_palette = false;
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switch ( dib_hdr_ptr->bpp ) {
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case 32: n_dst_chans = n_src_chans = 4; break; // technically can be RGB but not supported
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case 24: n_dst_chans = n_src_chans = 3; break; // technically can be RGBA but not supported
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case 8: // seems to always use a BGR0 palette, even for greyscale
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n_dst_chans = 3;
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has_palette = true;
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n_src_chans = 1;
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break;
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case 4: // always has a palette - needed for a MS-saved BMP
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n_dst_chans = 3;
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has_palette = true;
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n_src_chans = 1;
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break;
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case 1: // 1-bpp means the palette has 3 colour channels with 2 colours i.e. monochrome but not always black & white
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n_dst_chans = 3;
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has_palette = true;
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n_src_chans = 1;
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break;
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default: // this includes 2bpp and 16bpp
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free( record.data );
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return NULL;
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} // endswitch
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*n_chans = n_dst_chans;
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// NOTE(Anton) some image formats are not allowed a palette - could check for a bad header spec here also
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if ( dib_hdr_ptr->n_colours_in_palette > 0 ) { has_palette = true; }
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#ifdef APG_BMP_DEBUG_OUTPUT
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printf( "apg_bmp_debug: reading image\n|-filename `%s`\n|-dims %ux%u pixels\n|-bpp %u\n|-n_src_chans %u\n|-n_dst_chans %u\n", filename, *w, *h,
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dib_hdr_ptr->bpp, n_src_chans, n_dst_chans );
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#endif
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uint32_t palette_offset = _BMP_FILE_HDR_SZ + dib_hdr_ptr->this_header_sz;
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bool has_bitmasks = false;
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if ( BI_BITFIELDS == dib_hdr_ptr->compression_method || BI_ALPHABITFIELDS == dib_hdr_ptr->compression_method ) {
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has_bitmasks = true;
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palette_offset += 12;
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}
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if ( palette_offset > record.sz ) {
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free( record.data );
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return NULL;
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}
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// work out if any padding how much to skip at end of each row
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uint32_t unpadded_row_sz = width * n_src_chans;
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// bit-encoded palette indices have different padding properties
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if ( 4 == dib_hdr_ptr->bpp ) {
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unpadded_row_sz = width % 2 > 0 ? width / 2 + 1 : width / 2; // find how many whole bytes required for this bit width
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}
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if ( 1 == dib_hdr_ptr->bpp ) {
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unpadded_row_sz = width % 8 > 0 ? width / 8 + 1 : width / 8; // find how many whole bytes required for this bit width
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}
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uint32_t row_padding_sz = 0 == unpadded_row_sz % 4 ? 0 : 4 - ( unpadded_row_sz % 4 ); // NOTE(Anton) didn't expect operator precedence of - over %
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// another file size integrity check: partially validate source image data size
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// 'image_data_offset' is by row padded to 4 bytes and is either colour data or palette indices.
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if ( file_hdr_ptr->image_data_offset + ( unpadded_row_sz + row_padding_sz ) * height > record.sz ) {
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free( record.data );
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return NULL;
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}
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// find which bit number each colour channel starts at, so we can separate colours out
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uint32_t bitshift_rgba[4] = {0, 0, 0, 0}; // NOTE(Anton) noticed this was int and not uint32_t so changed it. 17 Mar 2020
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uint32_t bitmask_a = 0;
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if ( has_bitmasks ) {
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bitmask_a = ~( dib_hdr_ptr->bitmask_r | dib_hdr_ptr->bitmask_g | dib_hdr_ptr->bitmask_b );
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bitshift_rgba[0] = _bitscan( dib_hdr_ptr->bitmask_r );
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bitshift_rgba[1] = _bitscan( dib_hdr_ptr->bitmask_g );
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bitshift_rgba[2] = _bitscan( dib_hdr_ptr->bitmask_b );
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bitshift_rgba[3] = _bitscan( bitmask_a );
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}
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// allocate memory for the output pixels block. cast to size_t in case width and height are both the max of 65536 and n_dst_chans > 1
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unsigned char* dst_img_ptr = malloc( (size_t)width * (size_t)height * (size_t)n_dst_chans );
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if ( !dst_img_ptr ) {
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free( record.data );
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return NULL;
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}
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uint8_t* palette_data_ptr = (uint8_t*)record.data + palette_offset;
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uint8_t* src_img_ptr = (uint8_t*)record.data + file_hdr_ptr->image_data_offset;
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size_t dst_stride_sz = width * n_dst_chans;
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// == 32-bpp -> 32-bit RGBA. == 32-bit and 16-bit require bitmasks
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if ( 32 == dib_hdr_ptr->bpp ) {
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// check source image has enough data in it to read from
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if ( (size_t)file_hdr_ptr->image_data_offset + (size_t)height * (size_t)width * (size_t)n_src_chans > record.sz ) {
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free( record.data );
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free( dst_img_ptr );
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return NULL;
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}
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size_t src_byte_idx = 0;
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for ( uint32_t r = 0; r < height; r++ ) {
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size_t dst_pixels_idx = r * dst_stride_sz;
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for ( uint32_t c = 0; c < width; c++ ) {
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uint32_t pixel;
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memcpy( &pixel, &src_img_ptr[src_byte_idx], 4 );
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// NOTE(Anton) the below assumes 32-bits is always RGBA 1 byte per channel. 10,10,10 RGB exists though and isn't handled.
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dst_img_ptr[dst_pixels_idx++] = ( uint8_t )( ( pixel & dib_hdr_ptr->bitmask_r ) >> bitshift_rgba[0] );
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dst_img_ptr[dst_pixels_idx++] = ( uint8_t )( ( pixel & dib_hdr_ptr->bitmask_g ) >> bitshift_rgba[1] );
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dst_img_ptr[dst_pixels_idx++] = ( uint8_t )( ( pixel & dib_hdr_ptr->bitmask_b ) >> bitshift_rgba[2] );
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dst_img_ptr[dst_pixels_idx++] = ( uint8_t )( ( pixel & bitmask_a ) >> bitshift_rgba[3] );
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src_byte_idx += 4;
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}
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src_byte_idx += row_padding_sz;
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}
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// == 8-bpp -> 24-bit RGB ==
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} else if ( 8 == dib_hdr_ptr->bpp && has_palette ) {
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// validate indices (body of image data) fits in file
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if ( file_hdr_ptr->image_data_offset + height * width > record.sz ) {
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free( record.data );
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free( dst_img_ptr );
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return NULL;
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}
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size_t src_byte_idx = 0;
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for ( uint32_t r = 0; r < height; r++ ) {
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size_t dst_pixels_idx = ( height - 1 - r ) * dst_stride_sz;
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for ( uint32_t c = 0; c < width; c++ ) {
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// "most palettes are 4 bytes in RGB0 order but 3 for..." - it was actually BRG0 in old images -- Anton
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uint8_t index = src_img_ptr[src_byte_idx]; // 8-bit index value per pixel
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if ( palette_offset + index * 4 + 2 >= record.sz ) {
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free( record.data );
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return dst_img_ptr;
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}
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dst_img_ptr[dst_pixels_idx++] = palette_data_ptr[index * 4 + 2];
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dst_img_ptr[dst_pixels_idx++] = palette_data_ptr[index * 4 + 1];
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dst_img_ptr[dst_pixels_idx++] = palette_data_ptr[index * 4 + 0];
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src_byte_idx++;
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}
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src_byte_idx += row_padding_sz;
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}
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// == 4-bpp (16-colour) -> 24-bit RGB ==
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} else if ( 4 == dib_hdr_ptr->bpp && has_palette ) {
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size_t src_byte_idx = 0;
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for ( uint32_t r = 0; r < height; r++ ) {
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size_t dst_pixels_idx = ( height - 1 - r ) * dst_stride_sz;
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for ( uint32_t c = 0; c < width; c++ ) {
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if ( file_hdr_ptr->image_data_offset + src_byte_idx > record.sz ) {
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free( record.data );
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free( dst_img_ptr );
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return NULL;
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}
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// handle 2 pixels at a time
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uint8_t pixel_duo = src_img_ptr[src_byte_idx];
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uint8_t a_index = ( 0xFF & pixel_duo ) >> 4;
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uint8_t b_index = 0xF & pixel_duo;
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if ( palette_offset + a_index * 4 + 2 >= record.sz ) { // invalid src image
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free( record.data );
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return dst_img_ptr;
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}
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if ( dst_pixels_idx + 3 > width * height * n_dst_chans ) { // done
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free( record.data );
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return dst_img_ptr;
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}
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dst_img_ptr[dst_pixels_idx++] = palette_data_ptr[a_index * 4 + 2];
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dst_img_ptr[dst_pixels_idx++] = palette_data_ptr[a_index * 4 + 1];
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dst_img_ptr[dst_pixels_idx++] = palette_data_ptr[a_index * 4 + 0];
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if ( ++c >= width ) { // advance a column
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c = 0;
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r++;
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if ( r >= height ) { // done. no need to get second pixel. eg a 1x1 pixel image.
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free( record.data );
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return dst_img_ptr;
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}
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dst_pixels_idx = ( height - 1 - r ) * dst_stride_sz;
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}
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if ( palette_offset + b_index * 4 + 2 >= record.sz ) { // invalid src image
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free( record.data );
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return dst_img_ptr;
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}
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if ( dst_pixels_idx + 3 > width * height * n_dst_chans ) { // done. probably redundant check since checking r >= height.
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free( record.data );
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return dst_img_ptr;
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}
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dst_img_ptr[dst_pixels_idx++] = palette_data_ptr[b_index * 4 + 2];
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dst_img_ptr[dst_pixels_idx++] = palette_data_ptr[b_index * 4 + 1];
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dst_img_ptr[dst_pixels_idx++] = palette_data_ptr[b_index * 4 + 0];
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src_byte_idx++;
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}
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src_byte_idx += row_padding_sz;
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}
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// == 1-bpp -> 24-bit RGB ==
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} else if ( 1 == dib_hdr_ptr->bpp && has_palette ) {
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/* encoding method for monochrome is not well documented.
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a 2x2 pixel image is stored as 4 1-bit palette indexes
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the palette is stored as any 2 RGB0 colours (not necessarily B&W)
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so for an image with indexes like so:
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1 1
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0 1
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it is bit-encoded as follows, starting at MSB:
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01000000 00000000 00000000 00000000 (first byte val 64)
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11000000 00000000 00000000 00000000 (first byte val 192)
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data is still split by row and each row padded to 4 byte multiples
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*/
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size_t src_byte_idx = 0;
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for ( uint32_t r = 0; r < height; r++ ) {
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uint8_t bit_idx = 0; // used in monochrome
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size_t dst_pixels_idx = ( height - 1 - r ) * dst_stride_sz;
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for ( uint32_t c = 0; c < width; c++ ) {
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if ( 8 == bit_idx ) { // start reading from the next byte
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src_byte_idx++;
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bit_idx = 0;
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}
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if ( file_hdr_ptr->image_data_offset + src_byte_idx > record.sz ) {
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free( record.data );
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return dst_img_ptr;
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}
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uint8_t pixel_oct = src_img_ptr[src_byte_idx];
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uint8_t bit = 128 >> bit_idx;
|
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uint8_t masked = pixel_oct & bit;
|
|
uint8_t palette_idx = masked > 0 ? 1 : 0;
|
|
|
|
if ( palette_offset + palette_idx * 4 + 2 >= record.sz ) {
|
|
free( record.data );
|
|
return dst_img_ptr;
|
|
}
|
|
dst_img_ptr[dst_pixels_idx++] = palette_data_ptr[palette_idx * 4 + 2];
|
|
dst_img_ptr[dst_pixels_idx++] = palette_data_ptr[palette_idx * 4 + 1];
|
|
dst_img_ptr[dst_pixels_idx++] = palette_data_ptr[palette_idx * 4 + 0];
|
|
bit_idx++;
|
|
}
|
|
src_byte_idx += ( row_padding_sz + 1 ); // 1bpp is special here
|
|
}
|
|
|
|
// == 24-bpp -> 24-bit RGB == (but also should handle some other n_chans cases)
|
|
} else {
|
|
// NOTE(Anton) this only supports 1 byte per channel
|
|
if ( file_hdr_ptr->image_data_offset + height * width * n_dst_chans > record.sz ) {
|
|
free( record.data );
|
|
free( dst_img_ptr );
|
|
return NULL;
|
|
}
|
|
size_t src_byte_idx = 0;
|
|
for ( uint32_t r = 0; r < height; r++ ) {
|
|
size_t dst_pixels_idx = ( height - 1 - r ) * dst_stride_sz;
|
|
for ( uint32_t c = 0; c < width; c++ ) {
|
|
// re-orders from BGR to RGB
|
|
if ( n_dst_chans > 3 ) { dst_img_ptr[dst_pixels_idx++] = src_img_ptr[src_byte_idx + 3]; }
|
|
if ( n_dst_chans > 2 ) { dst_img_ptr[dst_pixels_idx++] = src_img_ptr[src_byte_idx + 2]; }
|
|
if ( n_dst_chans > 1 ) { dst_img_ptr[dst_pixels_idx++] = src_img_ptr[src_byte_idx + 1]; }
|
|
dst_img_ptr[dst_pixels_idx++] = src_img_ptr[src_byte_idx];
|
|
src_byte_idx += n_src_chans;
|
|
}
|
|
src_byte_idx += row_padding_sz;
|
|
}
|
|
} // endif bpp
|
|
|
|
free( record.data );
|
|
return dst_img_ptr;
|
|
}
|
|
|
|
void apg_bmp_free( unsigned char* pixels_ptr ) {
|
|
if ( !pixels_ptr ) { return; }
|
|
free( pixels_ptr );
|
|
}
|
|
|
|
unsigned int apg_bmp_write( const char* filename, unsigned char* pixels_ptr, int w, int h, unsigned int n_chans ) {
|
|
if ( !filename || !pixels_ptr ) { return 0; }
|
|
if ( 0 == w || 0 == h ) { return 0; }
|
|
if ( labs( w ) > _BMP_MAX_DIMS || labs( h ) > _BMP_MAX_DIMS ) { return 0; }
|
|
if ( n_chans != 3 && n_chans != 4 ) { return 0; }
|
|
|
|
uint32_t height = (uint32_t)labs( h );
|
|
uint32_t width = (uint32_t)labs( w );
|
|
// work out if any padding how much to skip at end of each row
|
|
const size_t unpadded_row_sz = width * n_chans;
|
|
const size_t row_padding_sz = 0 == unpadded_row_sz % 4 ? 0 : 4 - unpadded_row_sz % 4;
|
|
const size_t row_sz = unpadded_row_sz + row_padding_sz;
|
|
const size_t dst_pixels_padded_sz = row_sz * height;
|
|
|
|
const size_t dib_hdr_sz = sizeof( _bmp_dib_BITMAPINFOHEADER_t );
|
|
_bmp_file_header_t file_hdr;
|
|
{
|
|
file_hdr.file_type[0] = 'B';
|
|
file_hdr.file_type[1] = 'M';
|
|
file_hdr.file_sz = _BMP_FILE_HDR_SZ + (uint32_t)dib_hdr_sz + (uint32_t)dst_pixels_padded_sz;
|
|
file_hdr.reserved1 = 0;
|
|
file_hdr.reserved2 = 0;
|
|
file_hdr.image_data_offset = _BMP_FILE_HDR_SZ + (uint32_t)dib_hdr_sz;
|
|
}
|
|
_bmp_dib_BITMAPINFOHEADER_t dib_hdr;
|
|
{
|
|
dib_hdr.this_header_sz = _BMP_MIN_DIB_HDR_SZ; // NOTE: must be 40 and not include the bitmask memory in size here
|
|
dib_hdr.w = w;
|
|
dib_hdr.h = h;
|
|
dib_hdr.n_planes = 1;
|
|
dib_hdr.bpp = 3 == n_chans ? 24 : 32;
|
|
dib_hdr.compression_method = 3 == n_chans ? BI_RGB : BI_BITFIELDS;
|
|
dib_hdr.image_uncompressed_sz = 0;
|
|
dib_hdr.horiz_pixels_per_meter = 0;
|
|
dib_hdr.vert_pixels_per_meter = 0;
|
|
dib_hdr.n_colours_in_palette = 0;
|
|
dib_hdr.n_important_colours = 0;
|
|
// big-endian masks. only used in BI_BITFIELDS and BI_ALPHABITFIELDS ( 16 and 32-bit images )
|
|
// important note: GIMP stores BMP data in this array order for 32-bit: [A][B][G][R]
|
|
dib_hdr.bitmask_r = 0xFF000000;
|
|
dib_hdr.bitmask_g = 0x00FF0000;
|
|
dib_hdr.bitmask_b = 0x0000FF00;
|
|
}
|
|
|
|
uint8_t* dst_pixels_ptr = malloc( dst_pixels_padded_sz );
|
|
if ( !dst_pixels_ptr ) { return 0; }
|
|
{
|
|
size_t dst_byte_idx = 0;
|
|
uint8_t padding[4] = {0, 0, 0, 0};
|
|
uint8_t rgba[4] = {0, 0, 0, 0};
|
|
uint8_t bgra[4] = {0, 0, 0, 0};
|
|
|
|
for ( uint32_t row = 0; row < height; row++ ) {
|
|
size_t src_byte_idx = ( height - 1 - row ) * n_chans * width;
|
|
for ( uint32_t col = 0; col < width; col++ ) {
|
|
for ( uint32_t chan = 0; chan < n_chans; chan++ ) { rgba[chan] = pixels_ptr[src_byte_idx++]; }
|
|
if ( 3 == n_chans ) {
|
|
bgra[0] = rgba[2];
|
|
bgra[1] = rgba[1];
|
|
bgra[2] = rgba[0];
|
|
} else {
|
|
/* NOTE(Anton) RGBA with alpha channel would be better supported with an extended DIB header */
|
|
bgra[0] = rgba[3];
|
|
bgra[1] = rgba[2];
|
|
bgra[2] = rgba[1];
|
|
bgra[3] = rgba[0]; // alpha
|
|
}
|
|
memcpy( &dst_pixels_ptr[dst_byte_idx], bgra, n_chans );
|
|
dst_byte_idx += (size_t)n_chans;
|
|
} // endfor col
|
|
if ( row_padding_sz > 0 ) {
|
|
memcpy( &dst_pixels_ptr[dst_byte_idx], padding, row_padding_sz );
|
|
dst_byte_idx += row_padding_sz;
|
|
}
|
|
} // endfor row
|
|
}
|
|
{
|
|
FILE* fp = fopen( filename, "wb" );
|
|
if ( !fp ) {
|
|
free( dst_pixels_ptr );
|
|
return 0;
|
|
}
|
|
if ( 1 != fwrite( &file_hdr, _BMP_FILE_HDR_SZ, 1, fp ) ) {
|
|
free( dst_pixels_ptr );
|
|
fclose( fp );
|
|
return 0;
|
|
}
|
|
if ( 1 != fwrite( &dib_hdr, dib_hdr_sz, 1, fp ) ) {
|
|
free( dst_pixels_ptr );
|
|
fclose( fp );
|
|
return 0;
|
|
}
|
|
if ( 1 != fwrite( dst_pixels_ptr, dst_pixels_padded_sz, 1, fp ) ) {
|
|
free( dst_pixels_ptr );
|
|
fclose( fp );
|
|
return 0;
|
|
}
|
|
fclose( fp );
|
|
}
|
|
free( dst_pixels_ptr );
|
|
|
|
return 1;
|
|
}
|