Windows 8 学习笔记（二十三）--WritableBitmap的读写操作C++

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在开发中，涉及图片的处理经常需要用到WritableBitmap对象，这个对象可以直接作为数据源赋值给Image控件，但若要保存这个对象，我们只能将其序列化保存为一个图片文件，自然需要用到图片的编解码库：

将WritableBitmap保存为图片文件

WriteableBitmap^ wb =“您的源”；
IBuffer^ buffer = wb->PixelBuffer;
DataReader^ dataReader = DataReader::FromBuffer(buffer);
Array^ fileContent =ref new Array(buffer->Length);
dataReader->ReadBytes(fileContent);
task(ApplicationData::Current->LocalFolder->CreateFileAsync(pathName, CreationCollisionOption::ReplaceExisting)).then([this,fileContent,wb](StorageFile^ file)
{  
task(file->OpenAsync(FileAccessMode::ReadWrite)).then([this,fileContent,wb](IRandomAccessStream^ _stream)
{
task(BitmapEncoder::CreateAsync(BitmapEncoder::JpegEncoderId,_stream)).then([this,fileContent,wb](BitmapEncoder^ encoder)
{
encoder->SetPixelData(BitmapPixelFormat::Bgra8,BitmapAlphaMode::Straight,wb->PixelWidth ,wb->PixelHeight,96,96,fileContent);
task(encoder->FlushAsync()).then([=](void)
{
//Jpeg File Save Success!
});
});
});
});

　　将图片文件读取到WritableBitmap对象



task  ReadTask(ApplicationData::Current->LocalFolder->GetFileAsync(filename));
ReadTask.then([=](StorageFile^ sampleFile)
{
task(sampleFile->OpenAsync(FileAccessMode::Read)).then([=](IRandomAccessStream^ readStream)
{
int nWidth = 163;
int nHeigh = 202;
WriteableBitmap^ bitmapSnap = ref new WriteableBitmap(nWidth,nHeigh);
readStream->Seek(0);
bitmapSnap->SetSource(readStream);
});
});