c# - Set secondary tile image from programatically created writeable bitmap -

i'm desperately trying set writeable bitmap source of secondary tiles image. think i'm there refuses work. can see i'm missing? grateful!

i'm creating bitmap using:

var bitmap = new writeablebitmap(150, 150);             stream stream = bitmap.pixelbuffer.asstream();             stream.seek(0, seekorigin.begin);              var pixels = new byte[stream.length];             (int = 0; < pixels.length; += 4)             {                 pixels[i] = 255;                 pixels[i + 1] = 0;                 pixels[i + 2] = 189;                 pixels[i + 3] = 9;             }              stream.write(pixels, 0, pixels.length);             bitmap.invalidate(); 

the image saved computer with:

await writeablebitmapsaveextensions.savetofile(bitmap, applicationdata.current.localfolder,"image.png", creationcollisionoption.replaceexisting); 

the image can found in directory:

c:\users\<user>\appdata\local\packages\<pkgid>\localstate  

i'm creating secondary tile using method:

createsecondarytilefromwebimage("image.png", "tildid","shortname","displayname","arguments", mainpage.getelementrect((frameworkelement)sender));  public async task createsecondarytilefromwebimage(string bitmapname, string tileid, string shortname, string displayname, string arguments, rect selection)     {         //create uri         var bitmap = new uri(string.format("ms-appdata:///local/{0}", bitmapname));          //create tile         secondarytile secondarytile = new secondarytile(tileid, shortname, displayname, arguments, tileoptions.shownameonlogo, bitmap);          //confirm creation         await secondarytile.requestcreateforselectionasync(selection, windows.ui.popups.placement.above);     } 

the tile created , pinned startscreen image 100% transparent.

after correcting code produced valid .png file in directory mentioned here: c:\users\\appdata\local\packages\\localstate

it turns out simple problem how writing writeablebitmap pixels. although writeablebitmap data stream format argb, bytes need written backwards. in question, i'm actually assigning every pixel to: bgra = 255,0,189,9

where transparency byte set 9, making image 100% transparent , giving appearance didn't load correctly.

therefore, in order desired color, instead need write:

var pixels = new byte[stream.length];         (int = 0; < pixels.length; += 4)         {             pixels[i] = 9;             pixels[i + 1] = 189;             pixels[i + 2] = 0;             pixels[i + 3] = 255;         }