Dear Reader!
Android graphics is new to me and I can't get a solution for this
problem, even though I know the docs very well by now. What I wanna do
is to blend several overlapping bitmaps using a given operation like
xor or multiply. My app has a Spot class which has function to return
a generated Bitmap and a BitmapShader based on the Bitmap, plus an
attribute that stores a PorterDuff.Mode value. Could someone please
explain why the following code doesn't work? All I get is a black
empty screen, but no errors.
parts of the Spot class:
public final Bitmap toBitmap()
{
Bitmap out = Bitmap.createBitmap(width, height,
Bitmap.Config.ARGB_8888);
out.eraseColor(Color.TRANSPARENT);
Canvas layer = new Canvas(out);
RoundRectShape rr = new RoundRectShape(new float[]{2, 2, 2, 2, 2,
2, 2, 2}, null, null);
getPaint().setColor(color);
rr.draw(layer, getPaint());
return out;
}
public BitmapShader getShader()
{
return new BitmapShader(toBitmap(), Shader.TileMode.REPEAT,
Shader.TileMode.REPEAT);
}
...and my main View:
@Override
protected void onDraw(Canvas canvas)
{
Bitmap screen = Bitmap.createBitmap(canvas.getWidth(),
canvas.getHeight(), Bitmap.Config.ARGB_8888);
Spot spot;
Paint paint = new Paint();
Canvas spotLayers = new Canvas(screen);
for (int i=0, mi=spots.size(); i<mi; i++)
{
spot = getSpot(i);
if (i > 1)
paint.setShader(new ComposeShader(getSpot(i-1).getShader(),
spot.getShader(), spot.getXferMode()));
else
paint.setShader(spot.getShader());
spotLayers.drawPaint(paint);
}
canvas.drawColor(Color.BLACK);
canvas.drawBitmap(screen, 0, 0, null);
}
I've already browsed through the API examples and all reference pages
related to graphics, but still dunno what's up. Any help would be
great!
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