128 lines
3.4 KiB
C++
128 lines
3.4 KiB
C++
// BMP.cc
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// extracts/inserts data from/into .bmp file
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// Adapted by Josh Holtrop from the original access_bmp.c by gw
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// Supports reading and creating 24-bit color BMP images
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#include "BMP.h"
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#include <stdio.h>
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#include <iostream>
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using namespace std;
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BMP::BMP(const char * fileName)
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{
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open(fileName);
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}
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BMP::BMP(const char * fileName, int width, int height, unsigned char * data)
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{
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create(fileName, width, height, data);
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}
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BMP::~BMP()
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{
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if (m_fp != NULL)
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close();
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}
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bool BMP::open(const char * fileName)
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{
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size_t bytes_read;
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m_fp = fopen(fileName, "r+");
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if (m_fp != NULL)
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{
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// read file header
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bytes_read = fread(&m_header, sizeof(m_header), 1, m_fp);
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if (m_header.id[0] != 'B' || m_header.id[1] != 'M')
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{
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cerr << fileName << " does not appear to be a BMP file." << endl;
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fclose(m_fp);
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m_fp = NULL;
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}
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// read image information
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bytes_read = fread(&m_info, sizeof(m_info), 1, m_fp);
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}
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return (m_fp != NULL);
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}
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bool BMP::create(const char * fileName, int width, int height,
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unsigned char * data)
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{
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size_t bytes_written;
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m_fp = fopen(fileName, "w+");
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if (m_fp != NULL)
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{
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/* Initialize the header structure */
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m_header.id[0] = 'B';
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m_header.id[1] = 'M';
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int row_padding = (3 * width) & 0x3;
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if (row_padding)
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row_padding = 4 - row_padding;
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int row_bytes = (3 * width) + row_padding;
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m_header.file_size = sizeof(m_header) +
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sizeof(m_info) +
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row_bytes * height;
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m_header.reserved = 0;
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m_header.offset = sizeof(m_header) + sizeof(m_info);
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/* Initialize the information structure */
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m_info.header_size = 40;
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m_info.width = width;
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m_info.height = height;
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m_info.color_planes = 1;
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m_info.color_depth = 24;
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m_info.compression = 0;
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m_info.image_size = 0;
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m_info.xresolution = 2835;
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m_info.yresolution = 2835;
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m_info.num_colors = 0;
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m_info.num_important_colors = 0;
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/* write them to the file */
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bytes_written = fwrite(&m_header, sizeof(m_header), 1, m_fp);
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bytes_written = fwrite(&m_info, sizeof(m_info), 1, m_fp);
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unsigned int zero = 0;
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unsigned char * data_ptr = data + (3 * width) * (height - 1);
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for (int i = 0; i < height; i++)
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{
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bytes_written = fwrite(data_ptr, 3 * width, 1, m_fp);
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if (row_padding)
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bytes_written = fwrite(&zero, row_padding, 1, m_fp);
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data_ptr -= 3 * width;
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}
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}
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return (m_fp != NULL);
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}
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void BMP::read(unsigned char * buf)
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{
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size_t bytes_read;
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if (m_fp != NULL)
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{
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int row_data_bytes = 3 * m_info.width;
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int row_padding = row_data_bytes & 0x3;
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if (row_padding)
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row_padding = 4 - row_padding;
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fseek(m_fp,
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(m_header.offset != 0
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? m_header.offset
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: sizeof(m_header) + sizeof(m_info)),
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SEEK_SET);
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unsigned char * data_ptr = buf + row_data_bytes * (m_info.height - 1);
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for (int i = 0; i < m_info.height; i++)
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{
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bytes_read = fread(data_ptr, row_data_bytes, 1, m_fp);
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if (row_padding)
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fseek(m_fp, row_padding, SEEK_CUR);
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data_ptr -= row_data_bytes;
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}
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}
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}
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void BMP::close()
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{
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if (m_fp != NULL)
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fclose(m_fp);
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m_fp = NULL;
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}
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