how to make haxe nme preloader render bitmap with transparency

Question

I want to show image with alpha channel over preloader's background for flash target with haxe nme. This need seems to be common when it comes to a preloader.

I find several possible way to do that, but with out luck on any of them. Since I make a custom Preloader class which inherits default NMEPreloader, all my trails&errors are in this class.

Method #1 - nme.Assets approach - Runtime Error

I tried call Assets.loadBitmapData("assets/img/miniMoon.png")in Preloader's constructer. Error occur at run time:

[Fault] exception, information=ArgumentError: Error #2015: Invalid BitmapData.

with call stack:

flash.display::BitmapData/ctor
flash.display::BitmapData
NME_assets_img_minimoon_png1 at H:\MWHx\export\flash\haxe\ApplicationMain.hx:2053
Type$/createInstance at C:\Motion-Tween\haxe\std\flash\_std\Type.hx:136
nme.installer::Assets$/getBitmapData at H:\MWHx\export\flash\haxe\nme\installer\Assets.hx:721
Preloader at H:\MWHx\source\Preloader.hx:55
...

I wonder whether nme.Assets class is ready to use during preloading.

Method #2 Embed in Flash Way - Rendered without transparency

Throuth it's not NME's favor to use embed, I have tried this:

@:bitmap("assets/img/miniMoon.png") class BDmoon extends BitmapData {}
...
var moon:Bitmap;
...
moon = new Bitmap(new BDmoon(32,32,true,0x00000000));

It just runs and but the image shown with out transparency, all pixels with alpha 0 is rendered white against background.

As a further test, I use moon.alpha = 0.5; then I can see through the image. So maybe this is a problem of losing alpha channel values during embedding in nme.

A preloader with small animation or a tiny game can be fun. I hope there is a solution for this. Thanks!

references: NME forum topic : Embed Transparent Png Image

Answer 1

Sorry for this, but it's a problem of my OWN IMAGE FILE !

Since I don't know how to close the silly question to new answers. I put up a clean solution here.

If you want to use image in preloader, here is my code. Tested under NME 3.5.5.

 @:bitmap("assets/img/miniMoon.png") class BDmoon extends nme.display.BitmapData{}

class MyPreloader extends NMEPreloader 
{
    public var embedBmp:nme.display.Bitmap;
    public var bmpFromAssets:nme.display.Bitmap;

    public function new(){
        super();

        embedBmp = new nme.display.Bitmap(new BDmoon(64, 64, true));
        addChild(embedBmp);

        // Line below cause problem, nme.Assets not ready in preloader
        bmpFromAssets = new nme.display.Bitmap(Assets.getBitmapData("assets/img/miniMoon.png"));
        addChild(bmpFromAssets);
    }

    public override function onLoaded()
    {
        // dispatchEvent (new Event (Event.COMPLETE));
    }
}

Refer: http://haxeflixel.com/forum/help/nme-355-preloader-flash-error

Answer 2

The problem is

new BDmoon(32,32,true,0x00000000)

The last one 0x00000000 denotes the color to fill the transparent areas with black. Change it to

new BDmoon(32,32,true)

You can use the Assets class with this.

Assets.loadBitmapData("img/miniMoon.png")

i.e., omit the folder assets from the path.