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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.IntDef;
import android.annotation.NonNull;
import android.graphics.drawable.Drawable;
/**
* Helper interface for adding custom processing to an image.
*
* <p>The image being processed may be a {@link Drawable}, {@link Bitmap} or frame
* of an animated image produced by {@link ImageDecoder}. This is called before
* the requested object is returned.</p>
*
* <p>This custom processing also applies to image types that are otherwise
* immutable, such as {@link Bitmap.Config#HARDWARE}.</p>
*
* <p>On an animated image, the callback will only be called once, but the drawing
* commands will be applied to each frame, as if the {@code Canvas} had been
* returned by {@link Picture#beginRecording}.<p>
*
* <p>Supplied to ImageDecoder via {@link ImageDecoder#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}. A common effect is to add transparency
* to the corners to achieve rounded corners. That can be done with the
* following code:</p>
*
* <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;
* </code>
*
*
* @param canvas The {@link Canvas} to draw to.
* @return Opacity of the result after drawing.
* {@link 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 {@code PixelFormat.TRANSLUCENT}) or you forced the image to
* be opaque (e.g. by drawing everywhere with an opaque color and
* {@code PorterDuff.Mode.DST_OVER}, in which case you should return
* {@code PixelFormat.OPAQUE}).
* {@link 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} 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} (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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