android/graphics/BitmapFactory.java

/*
 * Copyright (C) 2007 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.content.res.AssetManager;
import android.content.res.Resources;
import android.util.DisplayMetrics;
import android.util.TypedValue;

import java.io.BufferedInputStream;
import java.io.FileDescriptor;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;

/**
 * Creates Bitmap objects from various sources, including files, streams,
 * and byte-arrays.
 */
public class BitmapFactory {
    public static class Options {
        /**
         * Create a default Options object, which if left unchanged will give
         * the same result from the decoder as if null were passed.
         */
        public Options() {
            inDither = false;
            inScaled = true;
        }

        /**
         * If set to true, the decoder will return null (no bitmap), but
         * the out... fields will still be set, allowing the caller to query
         * the bitmap without having to allocate the memory for its pixels.
         */
        public boolean inJustDecodeBounds;

        /**
         * If set to a value > 1, requests the decoder to subsample the original
         * image, returning a smaller image to save memory. The sample size is
         * the number of pixels in either dimension that correspond to a single
         * pixel in the decoded bitmap. For example, inSampleSize == 4 returns
         * an image that is 1/4 the width/height of the original, and 1/16 the
         * number of pixels. Any value <= 1 is treated the same as 1. Note: the
         * decoder will try to fulfill this request, but the resulting bitmap
         * may have different dimensions that precisely what has been requested.
         * Also, powers of 2 are often faster/easier for the decoder to honor.
         */
        public int inSampleSize;

        /**
         * If this is non-null, the decoder will try to decode into this
         * internal configuration. If it is null, or the request cannot be met,
         * the decoder will try to pick the best matching config based on the
         * system's screen depth, and characteristics of the original image such
         * as if it has per-pixel alpha (requiring a config that also does).
         *
         * Image are loaded with the {@link Bitmap.Config#ARGB_8888} config by
         * default.
         */
        public Bitmap.Config inPreferredConfig = Bitmap.Config.ARGB_8888;

        /**
         * If dither is true, the decoder will attempt to dither the decoded
         * image.
         */
        public boolean inDither;

        /**
         * The pixel density to use for the bitmap.  This will always result
         * in the returned bitmap having a density set for it (see
         * {@link Bitmap#setDensity(int) Bitmap.setDensity(int)}).  In addition,
         * if {@link #inScaled} is set (which it is by default} and this
         * density does not match {@link #inTargetDensity}, then the bitmap
         * will be scaled to the target density before being returned.
         *
         * <p>If this is 0,
         * {@link BitmapFactory#decodeResource(Resources, int)},
         * {@link BitmapFactory#decodeResource(Resources, int, android.graphics.BitmapFactory.Options)},
         * and {@link BitmapFactory#decodeResourceStream}
         * will fill in the density associated with the resource.  The other
         * functions will leave it as-is and no density will be applied.
         *
         * @see #inTargetDensity
         * @see #inScreenDensity
         * @see #inScaled
         * @see Bitmap#setDensity(int)
         * @see android.util.DisplayMetrics#densityDpi
         */
        public int inDensity;

        /**
         * The pixel density of the destination this bitmap will be drawn to.
         * This is used in conjunction with {@link #inDensity} and
         * {@link #inScaled} to determine if and how to scale the bitmap before
         * returning it.
         *
         * <p>If this is 0,
         * {@link BitmapFactory#decodeResource(Resources, int)},
         * {@link BitmapFactory#decodeResource(Resources, int, android.graphics.BitmapFactory.Options)},
         * and {@link BitmapFactory#decodeResourceStream}
         * will fill in the density associated the Resources object's
         * DisplayMetrics.  The other
         * functions will leave it as-is and no scaling for density will be
         * performed.
         *
         * @see #inDensity
         * @see #inScreenDensity
         * @see #inScaled
         * @see android.util.DisplayMetrics#densityDpi
         */
        public int inTargetDensity;

        /**
         * The pixel density of the actual screen that is being used.  This is
         * purely for applications running in density compatibility code, where
         * {@link #inTargetDensity} is actually the density the application
         * sees rather than the real screen density.
         *
         * <p>By setting this, you
         * allow the loading code to avoid scaling a bitmap that is currently
         * in the screen density up/down to the compatibility density.  Instead,
         * if {@link #inDensity} is the same as {@link #inScreenDensity}, the
         * bitmap will be left as-is.  Anything using the resulting bitmap
         * must also used {@link Bitmap#getScaledWidth(int)
         * Bitmap.getScaledWidth} and {@link Bitmap#getScaledHeight
         * Bitmap.getScaledHeight} to account for any different between the
         * bitmap's density and the target's density.
         *
         * <p>This is never set automatically for the caller by
         * {@link BitmapFactory} itself.  It must be explicitly set, since the
         * caller must deal with the resulting bitmap in a density-aware way.
         *
         * @see #inDensity
         * @see #inTargetDensity
         * @see #inScaled
         * @see android.util.DisplayMetrics#densityDpi
         */
        public int inScreenDensity;

        /**
         * When this flag is set, if {@link #inDensity} and
         * {@link #inTargetDensity} are not 0, the
         * bitmap will be scaled to match {@link #inTargetDensity} when loaded,
         * rather than relying on the graphics system scaling it each time it
         * is drawn to a Canvas.
         *
         * <p>This flag is turned on by default and should be turned off if you need
         * a non-scaled version of the bitmap.  Nine-patch bitmaps ignore this
         * flag and are always scaled.
         */
        public boolean inScaled;

        /**
         * If this is set to true, then the resulting bitmap will allocate its
         * pixels such that they can be purged if the system needs to reclaim
         * memory. In that instance, when the pixels need to be accessed again
         * (e.g. the bitmap is drawn, getPixels() is called), they will be
         * automatically re-decoded.
         *
         * For the re-decode to happen, the bitmap must have access to the
         * encoded data, either by sharing a reference to the input
         * or by making a copy of it. This distinction is controlled by
         * inInputShareable. If this is true, then the bitmap may keep a shallow
         * reference to the input. If this is false, then the bitmap will
         * explicitly make a copy of the input data, and keep that. Even if
         * sharing is allowed, the implementation may still decide to make a
         * deep copy of the input data.
         */
        public boolean inPurgeable;

        /**
         * This field works in conjuction with inPurgeable. If inPurgeable is
         * false, then this field is ignored. If inPurgeable is true, then this
         * field determines whether the bitmap can share a reference to the
         * input data (inputstream, array, etc.) or if it must make a deep copy.
         */
        public boolean inInputShareable;

        /**
         * Normally bitmap allocations count against the dalvik heap, which
         * means they help trigger GCs when a lot have been allocated. However,
         * in rare cases, the caller may want to allocate the bitmap outside of
         * that heap. To request that, set inNativeAlloc to true. In these
         * rare instances, it is solely up to the caller to ensure that OOM is
         * managed explicitly by calling bitmap.recycle() as soon as such a
         * bitmap is no longer needed.
         *
         * @hide pending API council approval
         */
        public boolean inNativeAlloc;

        /**
         * If inPreferQualityOverSpeed is set to true, the decoder will try to
         * decode the reconstructed image to a higher quality even at the
         * expense of the decoding speed. Currently the field only affects JPEG
         * decode, in the case of which a more accurate, but slightly slower,
         * IDCT method will be used instead.
         * @hide
         */
        public boolean inPreferQualityOverSpeed;

        /**
         * The resulting width of the bitmap, set independent of the state of
         * inJustDecodeBounds. However, if there is an error trying to decode,
         * outWidth will be set to -1.
         */

        public int outWidth;

        /**
         * The resulting height of the bitmap, set independent of the state of
         * inJustDecodeBounds. However, if there is an error trying to decode,
         * outHeight will be set to -1.
         */
        public int outHeight;

        /**
         * If known, this string is set to the mimetype of the decoded image.
         * If not know, or there is an error, it is set to null.
         */
        public String outMimeType;

        /**
         * Temp storage to use for decoding.  Suggest 16K or so.
         */
        public byte[] inTempStorage;

        private native void requestCancel();

        /**
         * Flag to indicate that cancel has been called on this object.  This
         * is useful if there's an intermediary that wants to first decode the
         * bounds and then decode the image.  In that case the intermediary
         * can check, inbetween the bounds decode and the image decode, to see
         * if the operation is canceled.
         */
        public boolean mCancel;

        /**
         *  This can be called from another thread while this options object is
         *  inside a decode... call. Calling this will notify the decoder that
         *  it should cancel its operation. This is not guaranteed to cancel
         *  the decode, but if it does, the decoder... operation will return
         *  null, or if inJustDecodeBounds is true, will set outWidth/outHeight
         *  to -1
         */
        public void requestCancelDecode() {
            mCancel = true;
            requestCancel();
        }
    }

    /**
     * Decode a file path into a bitmap. If the specified file name is null,
     * or cannot be decoded into a bitmap, the function returns null.
     *
     * @param pathName complete path name for the file to be decoded.
     * @param opts null-ok; Options that control downsampling and whether the
     *             image should be completely decoded, or just is size returned.
     * @return The decoded bitmap, or null if the image data could not be
     *         decoded, or, if opts is non-null, if opts requested only the
     *         size be returned (in opts.outWidth and opts.outHeight)
     */
    public static Bitmap decodeFile(String pathName, Options opts) {
        Bitmap bm = null;
        InputStream stream = null;
        try {
            stream = new FileInputStream(pathName);
            bm = decodeStream(stream, null, opts);
        } catch (Exception e) {
            /*  do nothing.
                If the exception happened on open, bm will be null.
            */
        } finally {
            if (stream != null) {
                try {
                    stream.close();
                } catch (IOException e) {
                    // do nothing here
                }
            }
        }
        return bm;
    }

    /**
     * Decode a file path into a bitmap. If the specified file name is null,
     * or cannot be decoded into a bitmap, the function returns null.
     *
     * @param pathName complete path name for the file to be decoded.
     * @return the resulting decoded bitmap, or null if it could not be decoded.
     */
    public static Bitmap decodeFile(String pathName) {
        return decodeFile(pathName, null);
    }

    /**
     * Decode a new Bitmap from an InputStream. This InputStream was obtained from
     * resources, which we pass to be able to scale the bitmap accordingly.
     */
    public static Bitmap decodeResourceStream(Resources res, TypedValue value,
            InputStream is, Rect pad, Options opts) {

        if (opts == null) {
            opts = new Options();
        }

        if (opts.inDensity == 0 && value != null) {
            final int density = value.density;
            if (density == TypedValue.DENSITY_DEFAULT) {
                opts.inDensity = DisplayMetrics.DENSITY_DEFAULT;
            } else if (density != TypedValue.DENSITY_NONE) {
                opts.inDensity = density;
            }
        }

        if (opts.inTargetDensity == 0 && res != null) {
            opts.inTargetDensity = res.getDisplayMetrics().densityDpi;
        }

        return decodeStream(is, pad, opts);
    }

    /**
     * Synonym for opening the given resource and calling
     * {@link #decodeResourceStream}.
     *
     * @param res   The resources object containing the image data
     * @param id The resource id of the image data
     * @param opts null-ok; Options that control downsampling and whether the
     *             image should be completely decoded, or just is size returned.
     * @return The decoded bitmap, or null if the image data could not be
     *         decoded, or, if opts is non-null, if opts requested only the
     *         size be returned (in opts.outWidth and opts.outHeight)
     */
    public static Bitmap decodeResource(Resources res, int id, Options opts) {
        Bitmap bm = null;
        InputStream is = null;

        try {
            final TypedValue value = new TypedValue();
            is = res.openRawResource(id, value);

            bm = decodeResourceStream(res, value, is, null, opts);
        } catch (Exception e) {
            /*  do nothing.
                If the exception happened on open, bm will be null.
                If it happened on close, bm is still valid.
            */
        } finally {
            try {
                if (is != null) is.close();
            } catch (IOException e) {
                // Ignore
            }
        }

        return bm;
    }

    /**
     * Synonym for {@link #decodeResource(Resources, int, android.graphics.BitmapFactory.Options)}
     * will null Options.
     *
     * @param res The resources object containing the image data
     * @param id The resource id of the image data
     * @return The decoded bitmap, or null if the image could not be decode.
     */
    public static Bitmap decodeResource(Resources res, int id) {
        return decodeResource(res, id, null);
    }

    /**
     * Decode an immutable bitmap from the specified byte array.
     *
     * @param data byte array of compressed image data
     * @param offset offset into imageData for where the decoder should begin
     *               parsing.
     * @param length the number of bytes, beginning at offset, to parse
     * @param opts null-ok; Options that control downsampling and whether the
     *             image should be completely decoded, or just is size returned.
     * @return The decoded bitmap, or null if the image data could not be
     *         decoded, or, if opts is non-null, if opts requested only the
     *         size be returned (in opts.outWidth and opts.outHeight)
     */
    public static Bitmap decodeByteArray(byte[] data, int offset, int length, Options opts) {
        if ((offset | length) < 0 || data.length < offset + length) {
            throw new ArrayIndexOutOfBoundsException();
        }
        return nativeDecodeByteArray(data, offset, length, opts);
    }

    /**
     * Decode an immutable bitmap from the specified byte array.
     *
     * @param data byte array of compressed image data
     * @param offset offset into imageData for where the decoder should begin
     *               parsing.
     * @param length the number of bytes, beginning at offset, to parse
     * @return The decoded bitmap, or null if the image could not be decode.
     */
    public static Bitmap decodeByteArray(byte[] data, int offset, int length) {
        return decodeByteArray(data, offset, length, null);
    }

    /**
     * Decode an input stream into a bitmap. If the input stream is null, or
     * cannot be used to decode a bitmap, the function returns null.
     * The stream's position will be where ever it was after the encoded data
     * was read.
     *
     * @param is The input stream that holds the raw data to be decoded into a
     *           bitmap.
     * @param outPadding If not null, return the padding rect for the bitmap if
     *                   it exists, otherwise set padding to [-1,-1,-1,-1]. If
     *                   no bitmap is returned (null) then padding is
     *                   unchanged.
     * @param opts null-ok; Options that control downsampling and whether the
     *             image should be completely decoded, or just is size returned.
     * @return The decoded bitmap, or null if the image data could not be
     *         decoded, or, if opts is non-null, if opts requested only the
     *         size be returned (in opts.outWidth and opts.outHeight)
     */
    public static Bitmap decodeStream(InputStream is, Rect outPadding, Options opts) {
        // we don't throw in this case, thus allowing the caller to only check
        // the cache, and not force the image to be decoded.
        if (is == null) {
            return null;
        }

        // we need mark/reset to work properly

        if (!is.markSupported()) {
            is = new BufferedInputStream(is, 16 * 1024);
        }

        // so we can call reset() if a given codec gives up after reading up to
        // this many bytes. FIXME: need to find out from the codecs what this
        // value should be.
        is.mark(1024);

        Bitmap  bm;

        if (is instanceof AssetManager.AssetInputStream) {
            bm = nativeDecodeAsset(((AssetManager.AssetInputStream) is).getAssetInt(),
                    outPadding, opts);
        } else {
            // pass some temp storage down to the native code. 1024 is made up,
            // but should be large enough to avoid too many small calls back
            // into is.read(...) This number is not related to the value passed
            // to mark(...) above.
            byte [] tempStorage = null;
            if (opts != null) tempStorage = opts.inTempStorage;
            if (tempStorage == null) tempStorage = new byte[16 * 1024];
            bm = nativeDecodeStream(is, tempStorage, outPadding, opts);
        }

        return finishDecode(bm, outPadding, opts);
    }

    private static Bitmap finishDecode(Bitmap bm, Rect outPadding, Options opts) {
        if (bm == null || opts == null) {
            return bm;
        }

        final int density = opts.inDensity;
        if (density == 0) {
            return bm;
        }

        bm.setDensity(density);
        final int targetDensity = opts.inTargetDensity;
        if (targetDensity == 0 || density == targetDensity || density == opts.inScreenDensity) {
            return bm;
        }

        byte[] np = bm.getNinePatchChunk();
        final boolean isNinePatch = np != null && NinePatch.isNinePatchChunk(np);
        if (opts.inScaled || isNinePatch) {
            float scale = targetDensity / (float)density;
            // TODO: This is very inefficient and should be done in native by Skia
            final Bitmap oldBitmap = bm;
            bm = Bitmap.createScaledBitmap(oldBitmap, (int) (bm.getWidth() * scale + 0.5f),
                    (int) (bm.getHeight() * scale + 0.5f), true);
            oldBitmap.recycle();

            if (isNinePatch) {
                np = nativeScaleNinePatch(np, scale, outPadding);
                bm.setNinePatchChunk(np);
            }
            bm.setDensity(targetDensity);
        }

        return bm;
    }

    /**
     * Decode an input stream into a bitmap. If the input stream is null, or
     * cannot be used to decode a bitmap, the function returns null.
     * The stream's position will be where ever it was after the encoded data
     * was read.
     *
     * @param is The input stream that holds the raw data to be decoded into a
     *           bitmap.
     * @return The decoded bitmap, or null if the image data could not be decoded.
     */
    public static Bitmap decodeStream(InputStream is) {
        return decodeStream(is, null, null);
    }

    /**
     * Decode a bitmap from the file descriptor. If the bitmap cannot be decoded
     * return null. The position within the descriptor will not be changed when
     * this returns, so the descriptor can be used again as-is.
     *
     * @param fd The file descriptor containing the bitmap data to decode
     * @param outPadding If not null, return the padding rect for the bitmap if
     *                   it exists, otherwise set padding to [-1,-1,-1,-1]. If
     *                   no bitmap is returned (null) then padding is
     *                   unchanged.
     * @param opts null-ok; Options that control downsampling and whether the
     *             image should be completely decoded, or just is size returned.
     * @return the decoded bitmap, or null
     */
    public static Bitmap decodeFileDescriptor(FileDescriptor fd, Rect outPadding, Options opts) {
        Bitmap bm = nativeDecodeFileDescriptor(fd, outPadding, opts);
        return finishDecode(bm, outPadding, opts);
    }

    /**
     * Decode a bitmap from the file descriptor. If the bitmap cannot be decoded
     * return null. The position within the descriptor will not be changed when
     * this returns, so the descriptor can be used again as is.
     *
     * @param fd The file descriptor containing the bitmap data to decode
     * @return the decoded bitmap, or null
     */
    public static Bitmap decodeFileDescriptor(FileDescriptor fd) {
        return decodeFileDescriptor(fd, null, null);
    }

    /**
     * Set the default config used for decoding bitmaps. This config is
     * presented to the codec if the caller did not specify a preferred config
     * in their call to decode...
     *
     * The default value is chosen by the system to best match the device's
     * screen and memory constraints.
     *
     * @param config The preferred config for decoding bitmaps. If null, then
     *               a suitable default is chosen by the system.
     *
     * @hide - only called by the browser at the moment, but should be stable
     *   enough to expose if needed
     */
    public static void setDefaultConfig(Bitmap.Config config) {
        if (config == null) {
            // pick this for now, as historically it was our default.
            // However, if we have a smarter algorithm, we can change this.
            config = Bitmap.Config.RGB_565;
        }
        nativeSetDefaultConfig(config.nativeInt);
    }

    private static native void nativeSetDefaultConfig(int nativeConfig);
    private static native Bitmap nativeDecodeStream(InputStream is, byte[] storage,
            Rect padding, Options opts);
    private static native Bitmap nativeDecodeFileDescriptor(FileDescriptor fd,
            Rect padding, Options opts);
    private static native Bitmap nativeDecodeAsset(int asset, Rect padding, Options opts);
    private static native Bitmap nativeDecodeByteArray(byte[] data, int offset,
            int length, Options opts);
    private static native byte[] nativeScaleNinePatch(byte[] chunk, float scale, Rect pad);
}