学步园

这个用了好多次了，在blog上记录一下吧

int SavePng(const string &png_file_name, byte **data, int width, int height, int bit_depth, png_colorp palette, int palette_len)<br /> {<br /> png_structp png_ptr;<br /> png_infop info_ptr;<br /> FILE *png_file = fopen(png_file_name.c_str(), "wb");<br /> assert(png_file);<br /> png_ptr = png_create_write_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);<br /> if(png_ptr == NULL)<br /> {<br /> cerr<<"ERROR:png_create_write_struct/n";<br /> return 0;<br /> }<br /> info_ptr = png_create_info_struct(png_ptr);<br /> if(info_ptr == NULL)<br /> {<br /> cerr<<"ERROR:png_create_info_struct/n";<br /> png_destroy_write_struct(&png_ptr, NULL);<br /> return 0;<br /> }<br /> png_init_io(png_ptr, png_file);<br /> png_set_IHDR(png_ptr, info_ptr, width, height, bit_depth, PNG_COLOR_TYPE_PALETTE,<br /> PNG_INTERLACE_NONE, PNG_COMPRESSION_TYPE_BASE, PNG_FILTER_TYPE_BASE);<br /> png_set_PLTE(png_ptr, info_ptr, palette, palette_len);<br /> png_write_info(png_ptr, info_ptr);<br /> //这里就是图像数据了<br /> png_bytepp row_pointers = new png_bytep[height];<br /> for (int i=0; i<height; ++i)<br /> {<br /> row_pointers[i] = (png_bytep)data[i];<br /> }<br /> png_write_image(png_ptr, row_pointers);<br /> delete row_pointers;<br /> png_write_end(png_ptr, info_ptr);<br /> png_free(png_ptr, palette);<br /> palette=NULL;<br /> png_destroy_write_struct(&png_ptr, &info_ptr);<br /> fclose(png_file);<br /> return 0;<br /> }<br /> void ReadPng(const string &png_file, byte *buf, byte real_bit_dep)<br /> {<br /> FILE *file = fopen(png_file.c_str(), "rb");<br /> assert(file);<br /> // create read struct<br /> png_structp png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);<br /> assert(png_ptr);<br /> // create info struct<br /> png_infop info_ptr = png_create_info_struct(png_ptr);<br /> assert(info_ptr);<br /> // I/O initialization using standard C streams<br /> png_init_io(png_ptr, file);<br /> // read entire image , ignore alpha channel<br /> png_read_png(png_ptr, info_ptr, PNG_TRANSFORM_IDENTITY|PNG_TRANSFORM_STRIP_ALPHA, NULL);<br /> int width = info_ptr->width;<br /> int height = info_ptr->height;<br /> int color_type = info_ptr->color_type;<br /> int bit_dep = info_ptr->pixel_depth;<br /> //这里要注意任何小于8bpp的图像被ps打开后都会被默认保存成8bpp的格式<br /> if (bit_dep < 8)<br /> {<br /> png_destroy_read_struct(&png_ptr, &info_ptr, 0);<br /> fclose(file);<br /> return;<br /> }<br /> uint line_bytes = (uint)(width*bit_dep/8.0);<br /> printf("%d %d %d line_bytes=%d/n", width, height, bit_dep, line_bytes);<br /> //read pic data<br /> png_bytep* row_pointers = png_get_rows(png_ptr,info_ptr);<br /> uint real_line_bytes = (uint)(width*real_bit_dep/8.0);<br /> byte* real_ptr = new byte[real_line_bytes];<br /> //write data to buf<br /> uint buf_offset = 0;<br /> printf("real_bit_dep = %d/n", real_bit_dep);<br /> for (int i=0; i<height; ++i)<br /> {<br /> //2bpp的情况<br /> if (real_bit_dep == 2)<br /> {</p> <p> for (uint j=0, t=0; j<real_line_bytes; ++j, t+=4)<br /> {<br /> real_ptr[j] = ((row_pointers[i][t+3]&0x3)<<6) | ((row_pointers[i][t+2]&0x3)<<4) |<br /> ((row_pointers[i][t+1]&0x3)<<2) | (row_pointers[i][t]&0x3);<br /> }<br /> }<br /> //4bpp的情况<br /> else if (real_bit_dep == 4)<br /> {<br /> for (uint j=0, t=0; j<real_line_bytes; ++j, t+=2)<br /> real_ptr[j] = ((row_pointers[i][t+1]&0xF) << 4) | (row_pointers[i][t]&0xF);<br /> }<br /> memcpy(&buf[buf_offset], real_ptr, real_line_bytes);<br /> buf_offset += real_line_bytes;<br /> }<br /> // free memory<br /> png_destroy_read_struct(&png_ptr, &info_ptr, 0);<br /> // close file<br /> fclose(file);<br /> }