How to create a single-color Bitmap to display a given hue? - windows-8

Question

I have a requirement to create an image based on a certain color. The color will vary and so will the size of the output image. I want to create the Bitmap and save it to the app's temporary folder. How do I do this?
My initial requirement came from a list of colors, and providing a sample of the color in the UI. If the size of the image is variable then I can create them for certain scenarios like result suggestions in the search pane.

Answer 1

This isn't easy. But it's all wrapped in this single method for you to use. I hope it helps. ANyway, here's the code to create a Bitmap based on a given color & size:
private async System.Threading.Tasks.Task<Windows.Storage.StorageFile> CreateThumb(Windows.UI.Color color, Windows.Foundation.Size size)
{
// create colored bitmap
var _Bitmap = new Windows.UI.Xaml.Media.Imaging.WriteableBitmap((int)size.Width, (int)size.Height);
byte[] _Pixels = new byte[4 * _Bitmap.PixelWidth * _Bitmap.PixelHeight];
for (int i = 0; i < _Pixels.Length; i += 4)
{
_Pixels[i + 0] = color.B;
_Pixels[i + 1] = color.G;
_Pixels[i + 2] = color.R;
_Pixels[i + 3] = color.A;
}
// update bitmap data
// using System.Runtime.InteropServices.WindowsRuntime;
using (var _Stream = _Bitmap.PixelBuffer.AsStream())
{
_Stream.Seek(0, SeekOrigin.Begin);
_Stream.Write(_Pixels, 0, _Pixels.Length);
_Bitmap.Invalidate();
}
// determine destination
var _Folder = Windows.Storage.ApplicationData.Current.TemporaryFolder;
var _Name = color.ToString().TrimStart('#') + ".png";
// use existing if already
Windows.Storage.StorageFile _File;
try { return await _Folder.GetFileAsync(_Name); }
catch { /* do nothing; not found */ }
_File = await _Folder.CreateFileAsync(_Name, Windows.Storage.CreationCollisionOption.ReplaceExisting);
// extract stream to write
// using System.Runtime.InteropServices.WindowsRuntime;
using (var _Stream = _Bitmap.PixelBuffer.AsStream())
{
_Pixels = new byte[(uint)_Stream.Length];
await _Stream.ReadAsync(_Pixels, 0, _Pixels.Length);
}
// write file
using (var _WriteStream = await _File.OpenAsync(Windows.Storage.FileAccessMode.ReadWrite))
{
var _Encoder = await Windows.Graphics.Imaging.BitmapEncoder
.CreateAsync(Windows.Graphics.Imaging.BitmapEncoder.PngEncoderId, _WriteStream);
_Encoder.SetPixelData(Windows.Graphics.Imaging.BitmapPixelFormat.Bgra8,
Windows.Graphics.Imaging.BitmapAlphaMode.Premultiplied,
(uint)_Bitmap.PixelWidth, (uint)_Bitmap.PixelHeight, 96, 96, _Pixels);
await _Encoder.FlushAsync();
using (var outputStream = _WriteStream.GetOutputStreamAt(0))
await outputStream.FlushAsync();
}
return _File;
}
Best of luck!