怎么封装libjpeg格式转换的方法
时间: 2024-05-05 15:16:09 浏览: 10
1. 设计函数接口:需要考虑输入输出参数、返回值、异常处理等问题,例如:
```c++
bool convertToJpeg(const char* inputPath, const char* outputPath);
```
2. 实现函数功能:根据函数接口设计,编写实现代码,例如:
```c++
#include <stdio.h>
#include <jpeglib.h>
bool convertToJpeg(const char* inputPath, const char* outputPath) {
FILE* infile = fopen(inputPath, "rb");
if (!infile) {
return false;
}
FILE* outfile = fopen(outputPath, "wb");
if (!outfile) {
fclose(infile);
return false;
}
struct jpeg_decompress_struct cinfo;
struct jpeg_error_mgr jerr;
cinfo.err = jpeg_std_error(&jerr);
jpeg_create_decompress(&cinfo);
jpeg_stdio_src(&cinfo, infile);
jpeg_read_header(&cinfo, TRUE);
jpeg_start_decompress(&cinfo);
JSAMPROW buffer;
buffer = new JSAMPLE[cinfo.output_width * cinfo.output_components];
while (cinfo.output_scanline < cinfo.output_height) {
buffer = &buffer[cinfo.output_width * cinfo.output_components];
jpeg_read_scanlines(&cinfo, &buffer, 1);
fwrite(buffer, 1, cinfo.output_width * cinfo.output_components, outfile);
}
jpeg_finish_decompress(&cinfo);
jpeg_destroy_decompress(&cinfo);
fclose(infile);
fclose(outfile);
delete[] buffer;
return true;
}
```
3. 提供头文件和库文件:将实现代码封装到一个头文件中,并提供相应的库文件,方便其他程序调用。例如:
```c++
// jpegconverter.h
#ifndef __JPEG_CONVERTER_H__
#define __JPEG_CONVERTER_H__
#include <stdbool.h>
#ifdef __cplusplus
extern "C" {
#endif
bool convertToJpeg(const char* inputPath, const char* outputPath);
#ifdef __cplusplus
}
#endif
#endif // __JPEG_CONVERTER_H__
// libjpegconverter.a
$ gcc -c jpegconverter.cpp
$ ar rcs libjpegconverter.a jpegconverter.o
```
4. 使用方法:在其他程序中引入头文件,并链接库文件,调用函数即可实现转换。例如:
```c++
#include <stdio.h>
#include "jpegconverter.h"
int main(int argc, char** argv) {
if (argc < 3) {
printf("Usage: %s input output\n", argv[0]);
return 1;
}
if (convertToJpeg(argv[1], argv[2])) {
printf("Convert success!\n");
} else {
printf("Convert failed!\n");
}
return 0;
}
```