C++/CX如何将IRandomAccessStream ^转换为字节和后端。 (UWP)
问题描述:
所以我有一个流,我希望能够将它转换为无符号的char *字节并返回到可用的流。C++/CX如何将IRandomAccessStream ^转换为字节和后端。 (UWP)
此流的图像(它是二进制的,如果它是重要的?)
基本上,我想现在是如下:
IRandomAccessStream^ inputStream;
DataWriter^ dataWriter = ref new DataWriter(inputStream);
IBuffer^ buffer1 = dataWriter->DetachBuffer();
unsigned char * bytes = GetPointerToPixelData(buffer1);
DataWriter ^writer = ref new DataWriter();
writer->WriteBytes(Platform::ArrayReference<BYTE>(bytes, sizeof(bytes)));
task<DataWriterStoreOperation^>(writer->StoreAsync()).get();
task<Windows::Foundation::IAsyncOperation<bool>>(writer->FlushAsync()).get();
IBuffer ^buffer2 = writer->DetachBuffer();
IRandomAccessStream^ newStream;
task<Windows::Foundation::IAsyncOperationWithProgress<unsigned int, unsigned int>>(newStream->WriteAsync(buffer2)).get();
task<Windows::Foundation::IAsyncOperation<bool>>(newStream->FlushAsync()).get();
UseNewStream(newStream)
我添加了所有这些任务<的... >因为没有它们就无法工作,我不知道如何使它工作? 我在网上找到与功能GetPointerToPixelData是以下几点:
byte* GetPointerToPixelData(IBuffer^ buffer)
{
// Cast to Object^, then to its underlying IInspectable interface.
Object^ obj = buffer;
ComPtr<IInspectable> insp(reinterpret_cast<IInspectable*>(obj));
// Query the IBufferByteAccess interface.
ComPtr<IBufferByteAccess> bufferByteAccess;
insp.As(&bufferByteAccess);
// Retrieve the buffer data.
byte* pixels = nullptr;
bufferByteAccess->Buffer(&pixels);
return pixels;
}
谢谢! :)
答
首先,如果要将图像流转换为字节,则需要通过DataReader
读取流,而不是通过用于写入数据的DataWriter
读取。其次,DetachBuffer()
方法用于“分离与数据读取器关联的缓冲区”,而不读取缓冲区。最后,DataReader
可以通过ReadBytes(Byte[])
方法直接读取字节。例如:
uint64 length = 0;
BYTE *extracted;
void CleanImagetobyte::MainPage::btnconverttobyte_Click(Platform::Object^ sender, Windows::UI::Xaml::RoutedEventArgs^ e)
{
create_task(KnownFolders::GetFolderForUserAsync(nullptr /* current user */, KnownFolderId::PicturesLibrary))
.then([this](StorageFolder^ picturesFolder)
{
return picturesFolder->GetFileAsync("B.jpg");
}).then([this](task<StorageFile^> task)
{
try
{
StorageFile^ file = task.get();
auto name = file->Name;
return file->OpenAsync(FileAccessMode::Read);
}
catch (Exception^ e)
{
// I/O errors are reported as exceptions.
}
}).then([this](task<IRandomAccessStream^> task)
{
IRandomAccessStream^ inputStream = task.get();
length = inputStream->Size;
IBuffer^ buffer = ref new Buffer(inputStream->Size);
inputStream->ReadAsync(buffer, inputStream->Size, InputStreamOptions::None);
DataReader^ reader = DataReader::FromBuffer(buffer);
extracted = new BYTE[buffer->Length];
reader->ReadBytes(Platform::ArrayReference<BYTE>(extracted, buffer->Length));
});
}
void CleanImagetobyte::MainPage::btnconvertback_Click(Platform::Object^ sender, Windows::UI::Xaml::RoutedEventArgs^ e)
{
create_task(KnownFolders::GetFolderForUserAsync(nullptr /* current user */, KnownFolderId::PicturesLibrary))
.then([this](StorageFolder^ picturesFolder)
{
return picturesFolder->CreateFileAsync("newB.jpg", CreationCollisionOption::ReplaceExisting);
}).then([this](task<StorageFile^> task)
{
StorageFile^ file = task.get();
Array<byte>^ arr = ref new Array<byte>(extracted, length);
FileIO::WriteBytesAsync(file, arr);
});
}
更多读写文件的详细信息请参考this document。