在C++中，可以使用第三方库如libpng、OpenCV等来实现bitmap的压缩与解压。下面是一个使用libpng库进行bitmap压缩与解压的示例代码：
#include <iostream>#include <png.h>void compressBitmap(const char* inputFile, const char* outputFile) { FILE *fp = fopen(inputFile, "rb"); if (!fp) { std::cerr << "Error opening input file" << std::endl; return; } png_structp png = png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL); if (!png) { std::cerr << "Error creating read struct" << std::endl; fclose(fp); return; } png_infop info = png_create_info_struct(png); if (!info) { std::cerr << "Error creating info struct" << std::endl; png_destroy_read_struct(&png, NULL, NULL); fclose(fp); return; } png_init_io(png, fp); png_read_info(png, info); png_set_compression_level(png, Z_BEST_COMPRESSION); FILE *out = fopen(outputFile, "wb"); if (!out) { std::cerr << "Error opening output file" << std::endl; png_destroy_read_struct(&png, &info, NULL); fclose(fp); return; } png_set_write_fn(png, out, [](png_structp png, png_bytep data, size_t length) { fwrite(data, 1, length, (FILE *)png_get_io_ptr(png)); }, NULL); png_write_info(png, info); png_bytep row = new png_byte[png_get_rowbytes(png, info)]; for (int y = 0; y < png_get_image_height(png, info); y++) { png_read_row(png, row, NULL); png_write_row(png, row); } png_write_end(png, NULL); delete[] row; fclose(out); png_destroy_read_struct(&png, &info, NULL); fclose(fp); std::cout << "Bitmap compressed successfully" << std::endl;}void decompressBitmap(const char* inputFile, const char* outputFile) { FILE *fp = fopen(inputFile, "rb"); if (!fp) { std::cerr << "Error opening input file" << std::endl; return; } png_structp png = png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL); if (!png) { std::cerr << "Error creating read struct" << std::endl; fclose(fp); return; } png_infop info = png_create_info_struct(png); if (!info) { std::cerr << "Error creating info struct" << std::endl; png_destroy_read_struct(&png, NULL, NULL); fclose(fp); return; } png_init_io(png, fp); png_read_info(png, info); FILE *out = fopen(outputFile, "wb"); if (!out) { std::cerr << "Error opening output file" << std::endl; png_destroy_read_struct(&png, &info, NULL); fclose(fp); return; } png_set_read_fn(png, out, [](png_structp png, png_bytep data, size_t length) { fread(data, 1, length, (FILE *)png_get_io_ptr(png)); }, NULL); png_read_end(png, NULL); png_bytep row = new png_byte[png_get_rowbytes(png, info)]; for (int y = 0; y < png_get_image_height(png, info); y++) { png_read_row(png, row, NULL); } delete[] row; fclose(out); png_destroy_read_struct(&png, &info, NULL); fclose(fp); std::cout << "Bitmap decompressed successfully" << std::endl;}int main() { compressBitmap("input.bmp", "compressed.png"); decompressBitmap("compressed.png", "output.bmp"); return 0;}在上面的示例中，我们使用libpng库来实现了对bitmap文件的压缩和解压缩操作。首先，我们使用compressBitmap函数来将输入的bitmap文件压缩成png文件，然后使用decompressBitmap函数将压缩后的png文件解压缩成bitmap文件。最后，在main函数中我们调用这两个函数来演示整个过程。
