Translate the BitmapEncoder code example in C++ please

Question

In my app, I need to save the on-screen rendering content to an image file and plan to use BitmapEncode class after some Bing searches.

This article titled "How to encode a new image (Windows Store apps using C#/VB/C++ and XAML)" provides a good example but unfortunately the code is C#, which cannot be used in my C++ app. I could not translate the code to C++ as there are two asyncronous tasks (file.OpenAsync and BitmapEncoder.CreateAsync) in the code. Could someone kindly to rewrite the code in C++? Thanks! Oh, another plea to Microsoft, could you give C++ code in your MSDN articles? we are tired of reading C#.

Answer 1

Here you go:

I added the following namespaces to a blank app page template.

using namespace Windows::Storage;
using namespace Windows::Storage::Pickers;
using namespace Windows::Storage::Provider;
using namespace Windows::Storage::Streams;
using namespace concurrency;

Added #include <ppltasks.h> to make the async work

void SimpleImageEncode::MainPage::EncodeImage()
{
	FileSavePicker^ savePicker = ref new FileSavePicker(); 
	auto plainTextExtensions = ref new Platform::Collections::Vector<String^>(); 
	plainTextExtensions->Append(".jpg"); 
	savePicker->FileTypeChoices->Insert("JPEG Image", plainTextExtensions); 
	savePicker->SuggestedFileName = "MyImage"; 
	savePicker->SuggestedStartLocation = PickerLocationId::Desktop; 

	create_task(savePicker->PickSaveFileAsync()).then([this](StorageFile^ file) 
	{ 
		if(file)
		{
			create_task(file->OpenAsync(Windows::Storage::FileAccessMode::ReadWrite)).then([this](IRandomAccessStream^ stream)
			{
				auto encoderId = Windows::Graphics::Imaging::BitmapEncoder::JpegEncoderId;
				stream->Size = 0;

				create_task(Windows::Graphics::Imaging::BitmapEncoder::CreateAsync(
					encoderId,
					stream
					)).then([this](Windows::Graphics::Imaging::BitmapEncoder^ encoder)
				{
					// An array representing 2x2 red, opaque pixel data
					Array<byte>^ pixels = {			
						255, 0, 0, 255,
						255, 0, 0, 255,
						255, 0, 0, 255,
						255, 0, 0, 255
					};

					encoder->SetPixelData(
						Windows::Graphics::Imaging::BitmapPixelFormat::Rgba8,
						Windows::Graphics::Imaging::BitmapAlphaMode::Straight,
						2, // pixel width
						2, // pixel height
						96, // horizontal DPI
						96, // vertical DPI
						pixels
						);
					encoder->FlushAsync();
				});
			});
		}
	});
}

Answer 2

Thank you very much jrboddie.