Why is this making a blank Bitmap?

Your problem is this line:

myBitmapData.setPixel32(j,i,0x000000); 

Here, you are setting the transparency to 0. Try:

myBitmapData.setPixel32(j,i,0xFF000000); 

You are drawing transparent black pixels. Instead of 0x000000 it should be 0xff000000.

myBitmapData.setPixel32(j,i,0xff000000);

or use setPixel(x, y, color);