c++ png

    关于bmp图片转换png

    以下是一个将c++截屏的位图信息转换成png数据的代码实现。

#include "stdafx.h"
#include "WindowsCommand.h"
#include <afxwin.h>
#include "atlimage.h"


/*
 * Class:     org_shine_network_windows_command_WindowsCommand
 * Method:    getScreenpixels
 * Signature: (I)[B
 */
JNIEXPORT jbyteArray JNICALL Java_org_shine_network_windows_command_WindowsCommand_getScreenpixels
	(JNIEnv * jniEnv, jobject, jint)
{
	
	//屏幕DC
	CDC *pDC;
	//获取当前整个屏幕DC
    pDC = CDC::FromHandle(GetDC(NULL));
	//获得颜色模式
    int BitPerPixel = pDC->GetDeviceCaps(BITSPIXEL);
    int Width = pDC->GetDeviceCaps(HORZRES);
    int Height = pDC->GetDeviceCaps(VERTRES);

    //内存DC
    CDC memDC;
    memDC.CreateCompatibleDC(pDC);
    //建立和屏幕兼容的bitmap
    CBitmap memBitmap, *oldmemBitmap;
    memBitmap.CreateCompatibleBitmap(pDC, Width, Height);
	//将memBitmap选入内存DC
    oldmemBitmap = memDC.SelectObject(&memBitmap);
	//复制屏幕图像到内存DC
    memDC.BitBlt(0, 0, Width, Height, pDC, 0, 0, SRCCOPY);

    //以下代码保存memDC中的位图到文件
    BITMAP bmp;
	//获得位图信息
    memBitmap.GetBitmap(&bmp);
    //位图信息头
    BITMAPINFOHEADER bih = {0};
	//每个像素字节大小
    bih.biBitCount = bmp.bmBitsPixel;
    bih.biCompression = BI_RGB;
	//高度
    bih.biHeight = bmp.bmHeight;
    bih.biPlanes = 1;
    bih.biSize = sizeof(BITMAPINFOHEADER);
	//图像数据大小
    bih.biSizeImage = bmp.bmWidthBytes * bmp.bmHeight;
	//宽度
    bih.biWidth = bmp.bmWidth;
    //位图文件头
    BITMAPFILEHEADER bfh = {0};
	//到位图数据的偏移量
    bfh.bfOffBits = sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER);
	//文件总的大小
    bfh.bfSize = bfh.bfOffBits + bmp.bmWidthBytes * bmp.bmHeight;
    bfh.bfType = (WORD)0x4d42;
    
	//bmp转换png方式	
    //申请内存保存位图数据
    byte * p = new byte[bmp.bmWidthBytes * bmp.bmHeight];
	//获取位图数据
    GetDIBits(memDC.m_hDC, (HBITMAP) memBitmap.m_hObject, 0, Height, p, (LPBITMAPINFO) &bih, DIB_RGB_COLORS);
	
	//////////////////////////////////////////////////
	/***  使用内存转换 **/
	
	//创建bmp流
	IStream* bmp_memory = NULL;
	//创建png流
	IStream* png_Memory = NULL;
	//申请一块bmp全局内存缓冲区
	HGLOBAL bmpHglobal = GlobalAlloc(GMEM_MOVEABLE,0);
	//申请一块png全局内存缓冲区
	HGLOBAL png_Hglobal = GlobalAlloc(GMEM_MOVEABLE,0);
	//将流与内存缓冲区关联
	CreateStreamOnHGlobal(bmpHglobal, TRUE, &bmp_memory);
	//将流与内存缓冲区关联
	CreateStreamOnHGlobal(png_Hglobal, TRUE, &png_Memory);

	//定义流数据
	LARGE_INTEGER zero = {0}; 
	ULARGE_INTEGER len = {0}; 

	//重置流起始位置
	bmp_memory->Seek(zero, STREAM_SEEK_SET, NULL);
	//写入位图文件头
	bmp_memory->Write(&bfh,sizeof(BITMAPFILEHEADER),NULL);
	//写入位图信息头
        bmp_memory->Write(&bih,  sizeof(BITMAPINFOHEADER),NULL);
	//写入位图数据
	bmp_memory->Write(p,bmp.bmWidthBytes * bmp.bmHeight,NULL);
	//重新定位到IStream头
	bmp_memory->Seek(zero, STREAM_SEEK_SET, NULL); 
	//创建image
	CImage *memoryImage = new CImage();
	//通过流加载image
	memoryImage->Load(bmp_memory);

	/*******************保存bmp为png************************************/
	//保存bmp为png
	memoryImage->Save(png_Memory,Gdiplus::ImageFormatPNG);
	//获取流数据长度
	png_Memory->Seek(zero, STREAM_SEEK_CUR, &len);
	
	//转换
	int size = unsigned long(len.LowPart);
	ULONG Readtotal = len.LowPart; 
	byte *data = new byte[size];
	//获取内存转换png数据
	ULONG uLongRet;
	png_Memory->Seek(zero, STREAM_SEEK_SET, NULL);
	png_Memory->Read(data,size,&uLongRet);
	
	//将本地字节数据转换成jni数据格式
	jbyteArray jbyteArray = jniEnv->NewByteArray(size);
	jbyte *jby = (jbyte*)data;
	jniEnv->SetByteArrayRegion(jbyteArray,0,size,jby);

	/**手动释放资源 */
	bmp_memory->Release(); 
    GlobalFree(bmp_memory); 
	png_Memory->Release();
	GlobalFree(png_Memory); 
	delete data;
	delete [] p;
	//释放
  memDC.SelectObject(oldmemBitmap);
	return jbyteArray;
}

   附件是java通过jni调用以上功能生成图片的实例。