90 lines
4.2 KiB
Java
90 lines
4.2 KiB
Java
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/*
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* Copyright (C) 2017 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package android.graphics;
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import android.annotation.NonNull;
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import android.graphics.drawable.AnimatedImageDrawable;
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import android.graphics.drawable.Drawable;
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/**
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* Helper interface for adding custom processing to an image.
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*
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* <p>The image being processed may be a {@link Drawable}, a {@link Bitmap}, or
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* a frame of an {@link AnimatedImageDrawable} produced by {@link ImageDecoder}.
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* This is called before the requested object is returned.</p>
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*
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* <p>This custom processing can even be applied to images that will be returned
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* as immutable objects, such as a {@link Bitmap} with {@code Config}
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* {@link Bitmap.Config#HARDWARE} returned by {@link ImageDecoder}.</p>
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*
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* <p>On an {@link AnimatedImageDrawable}, the callback will only be called once,
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* but the drawing commands will be applied to each frame, as if the {@link Canvas}
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* had been returned by {@link Picture#beginRecording Picture.beginRecording}.<p>
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*
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* <p>Supplied to ImageDecoder via {@link ImageDecoder#setPostProcessor setPostProcessor}.</p>
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*/
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public interface PostProcessor {
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/**
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* Do any processing after (for example) decoding.
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*
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* <p>Drawing to the {@link Canvas} will behave as if the initial processing
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* (e.g. decoding) already exists in the Canvas. An implementation can draw
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* effects on top of this, or it can even draw behind it using
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* {@link PorterDuff.Mode#DST_OVER PorterDuff.Mode.DST_OVER}. A common
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* effect is to add transparency to the corners to achieve rounded corners.
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* That can be done with the following code:</p>
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*
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* <pre class="prettyprint">
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* Path path = new Path();
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* path.setFillType(Path.FillType.INVERSE_EVEN_ODD);
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* int width = canvas.getWidth();
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* int height = canvas.getHeight();
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* path.addRoundRect(0, 0, width, height, 20, 20, Path.Direction.CW);
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* Paint paint = new Paint();
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* paint.setAntiAlias(true);
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* paint.setColor(Color.TRANSPARENT);
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* paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC));
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* canvas.drawPath(path, paint);
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* return PixelFormat.TRANSLUCENT;
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* </pre>
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*
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*
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* @param canvas The {@link Canvas} to draw to.
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* @return Opacity of the result after drawing.
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* {@link PixelFormat#UNKNOWN PixelFormat.UNKNOWN} means that the
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* implementation did not change whether the image has alpha. Return
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* this unless you added transparency (e.g. with the code above, in
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* which case you should return
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* {@link PixelFormat#TRANSLUCENT PixelFormat.TRANSLUCENT}) or you
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* forced the image to be opaque (e.g. by drawing everywhere with an
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* opaque color and {@link PorterDuff.Mode#DST_OVER PorterDuff.Mode.DST_OVER},
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* in which case you should return {@link PixelFormat#OPAQUE PixelFormat.OPAQUE}).
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* {@link PixelFormat#TRANSLUCENT PixelFormat.TRANSLUCENT} means that
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* the implementation added transparency. This is safe to return even
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* if the image already had transparency. This is also safe to return
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* if the result is opaque, though it may draw more slowly.
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* {@link PixelFormat#OPAQUE PixelFormat.OPAQUE} means that the
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* implementation forced the image to be opaque. This is safe to return
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* even if the image was already opaque.
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* {@link PixelFormat#TRANSPARENT PixelFormat.TRANSPARENT} (or any other
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* integer) is not allowed, and will result in throwing an
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* {@link java.lang.IllegalArgumentException}.
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*/
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@PixelFormat.Opacity
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public int onPostProcess(@NonNull Canvas canvas);
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}
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