PostProcessor
public
interface
PostProcessor
android.graphics.PostProcessor |
Helper interface for adding custom processing to an image.
The image being processed may be a Drawable
, a Bitmap
, or
a frame of an AnimatedImageDrawable
produced by ImageDecoder
.
This is called before the requested object is returned.
This custom processing can even be applied to images that will be returned
as immutable objects, such as a Bitmap
with Config
Bitmap.Config.HARDWARE
returned by ImageDecoder
.
On an AnimatedImageDrawable
, the callback will only be called once,
but the drawing commands will be applied to each frame, as if the Canvas
had been returned by Picture.beginRecording
.
Supplied to ImageDecoder via setPostProcessor
.
Summary
Public methods | |
---|---|
abstract
int
|
onPostProcess(Canvas canvas)
Do any processing after (for example) decoding. |
Public methods
onPostProcess
public abstract int onPostProcess (Canvas canvas)
Do any processing after (for example) decoding.
Drawing to the Canvas
will behave as if the initial processing
(e.g. decoding) already exists in the Canvas. An implementation can draw
effects on top of this, or it can even draw behind it using
PorterDuff.Mode.DST_OVER
. A common
effect is to add transparency to the corners to achieve rounded corners.
That can be done with the following code:
Path path = new Path(); path.setFillType(Path.FillType.INVERSE_EVEN_ODD); int width = canvas.getWidth(); int height = canvas.getHeight(); path.addRoundRect(0, 0, width, height, 20, 20, Path.Direction.CW); Paint paint = new Paint(); paint.setAntiAlias(true); paint.setColor(Color.TRANSPARENT); paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC)); canvas.drawPath(path, paint); return PixelFormat.TRANSLUCENT;
Parameters | |
---|---|
canvas |
Canvas : The Canvas to draw to.
This value cannot be null . |
Returns | |
---|---|
int |
Opacity of the result after drawing.
PixelFormat.UNKNOWN means that the
implementation did not change whether the image has alpha. Return
this unless you added transparency (e.g. with the code above, in
which case you should return
PixelFormat.TRANSLUCENT ) or you
forced the image to be opaque (e.g. by drawing everywhere with an
opaque color and PorterDuff.Mode.DST_OVER ,
in which case you should return PixelFormat.OPAQUE ).
PixelFormat.TRANSLUCENT means that
the implementation added transparency. This is safe to return even
if the image already had transparency. This is also safe to return
if the result is opaque, though it may draw more slowly.
PixelFormat.OPAQUE means that the
implementation forced the image to be opaque. This is safe to return
even if the image was already opaque.
PixelFormat.TRANSPARENT (or any other
integer) is not allowed, and will result in throwing an
IllegalArgumentException .
Value is PixelFormat.UNKNOWN , PixelFormat.TRANSLUCENT , PixelFormat.TRANSPARENT , or PixelFormat.OPAQUE |