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/*
* Copyright (C) 2017 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package android.graphics;
import android.annotation.NonNull;
import android.graphics.drawable.AnimatedImageDrawable;
import android.graphics.drawable.Drawable;
/**
* Helper interface for adding custom processing to an image.
*
* <p>The image being processed may be a {@link Drawable}, a {@link Bitmap}, or
* a frame of an {@link AnimatedImageDrawable} produced by {@link ImageDecoder}.
* This is called before the requested object is returned.</p>
*
* <p>This custom processing can even be applied to images that will be returned
* as immutable objects, such as a {@link Bitmap} with {@code Config}
* {@link Bitmap.Config#HARDWARE} returned by {@link ImageDecoder}.</p>
*
* <p>On an {@link AnimatedImageDrawable}, the callback will only be called once,
* but the drawing commands will be applied to each frame, as if the {@link Canvas}
* had been returned by {@link Picture#beginRecording Picture.beginRecording}.<p>
*
* <p>Supplied to ImageDecoder via {@link ImageDecoder#setPostProcessor setPostProcessor}.</p>
*/
public interface PostProcessor {
/**
* Do any processing after (for example) decoding.
*
* <p>Drawing to the {@link 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
* {@link PorterDuff.Mode#DST_OVER 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:</p>
*
* <pre class="prettyprint">
* 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;
* </pre>
*
*
* @param canvas The {@link Canvas} to draw to.
* @return Opacity of the result after drawing.
* {@link PixelFormat#UNKNOWN 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
* {@link PixelFormat#TRANSLUCENT PixelFormat.TRANSLUCENT}) or you
* forced the image to be opaque (e.g. by drawing everywhere with an
* opaque color and {@link PorterDuff.Mode#DST_OVER PorterDuff.Mode.DST_OVER},
* in which case you should return {@link PixelFormat#OPAQUE PixelFormat.OPAQUE}).
* {@link PixelFormat#TRANSLUCENT 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.
* {@link PixelFormat#OPAQUE PixelFormat.OPAQUE} means that the
* implementation forced the image to be opaque. This is safe to return
* even if the image was already opaque.
* {@link PixelFormat#TRANSPARENT PixelFormat.TRANSPARENT} (or any other
* integer) is not allowed, and will result in throwing an
* {@link java.lang.IllegalArgumentException}.
*/
@PixelFormat.Opacity
public int onPostProcess(@NonNull Canvas canvas);
}
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