利用CxImage实现编解码Gif图像代码举例

Gif(GraphicsInterchange Format，图形交换格式)是由CompuServe公司在1987年开发的图像文件格式，分为87a和89a两种版本。Gif是基于LZW算法的无损压缩算法。Gif图像是基于颜色表的，最多只支持8位(256色)。Gif减少了图像调色板中的色彩数量，从而在存储时达到减少图像文件大小的目的。Gif分为静态Gif和动画Gif两种，扩展名为.gif，是一种压缩位图格式，支持透明背景图像，适用于多种操作系统。

下面利用CxImage开源库，实现对Gif图像进行编解码，主要包括3个文件：

1. funset.h :

#ifndef _FUNSET_H_
#define _FUNSET_H_

#include <string>

using namespace std;

void decoding_gif(string strGifName, string strSavePath);
void encoding_gif(string strImgPath, string strGifName);

#endif //_FUNSET_H_

2. funset.cpp:

#include "stdafx.h"
#include "funset.h"
#include <iostream>
#include "../CxImage/ximagif.h"
#include <io.h>

using namespace std;

void decoding_gif(string strGifName, string strSavePath)
{
	CxImage img;

	img.Load(strGifName.c_str(), CXIMAGE_FORMAT_GIF);

	int iNumFrames = img.GetNumFrames();
	cout<<"frames num = "<<iNumFrames<<endl;

	CxImage* newImage = new CxImage();

	for (int i = 0; i < iNumFrames; i++) {
		newImage->SetFrame(i);
		newImage->Load(strGifName.c_str(), CXIMAGE_FORMAT_GIF);

		char tmp[64];
		sprintf(tmp, "%d", i);

		string tmp1;
		tmp1 = tmp1.insert(0, tmp);

		tmp1 = strSavePath + tmp1 + ".png";

		newImage->Save(tmp1.c_str(), CXIMAGE_FORMAT_PNG);
	}

	if (newImage) delete newImage;
}

int TraverseFolder(const string strFilePath, string strImageNameSets[])
{
	int iImageCount=0;

	_finddata_t fileInfo;

	long handle = _findfirst(strFilePath.c_str(), &fileInfo);

	if (handle == -1L) {
		cerr << "failed to transfer files" << endl;
		return -1;
	}

	do {
		//cout << fileInfo.name <<endl;
		strImageNameSets[iImageCount] = (string)fileInfo.name;

		iImageCount ++;

	} while (_findnext(handle, &fileInfo) == 0);

	return iImageCount;
}

void encoding_gif(string strImgPath, string strGifName)
{
	string strImgSets[100] = {};

	int iImgCount = TraverseFolder(strImgPath, strImgSets);

	string strTmp = strImgPath.substr(0, strImgPath.find_last_of("/") +1);

	CxImage** img = new CxImage*[iImgCount];
	if (img == NULL) {
		cout<<"new Cximage error!"<<endl;
		return;
	}

	for (int i = 0; i < iImgCount; i++) {
		string tmp1;
		tmp1 = strTmp + strImgSets[i];
		img[i] = new CxImage;
		img[i]->Load(tmp1.c_str(), CXIMAGE_FORMAT_PNG);
	}

	CxIOFile hFile;
	hFile.Open(strGifName.c_str(), "wb");

	CxImageGIF multiimage;

	multiimage.SetLoops(3);
	multiimage.SetDisposalMethod(2);
	multiimage.Encode(&hFile, img, iImgCount, false, false);

	hFile.Close();

	delete [] img;
}

3. main.cpp:

#include "stdafx.h"
#include <iostream>
#include "funset.h"

using namespace std;

int main(int argc, char* argv[])
{
	string strGifName = "../../Data/fire.gif";
	string strSavaPath = "../../Data/";

	decoding_gif(strGifName, strSavaPath);

	string strImgPath = "../../Data/*.png";
	strGifName = "../../Data/tmp.gif";

	encoding_gif(strImgPath, strGifName);

	cout<<"ok!!!"<<endl;

	return 0;
}

利用CxImage实现起来简单吧！！！^_^