Java tutorial
//package com.java2s; /* * Copyright (C) 2009 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. */ import android.graphics.Bitmap; import android.graphics.BitmapFactory; import android.graphics.Canvas; import android.graphics.Matrix; import android.graphics.Rect; import android.provider.MediaStore.Images; import android.util.Log; import java.io.FileInputStream; import java.io.FileDescriptor; import java.io.IOException; public class Main { private static final String TAG = "ThumbnailUtils"; private static final int MAX_NUM_PIXELS_THUMBNAIL = 512 * 384; private static final int MAX_NUM_PIXELS_MICRO_THUMBNAIL = 128 * 128; private static final int UNCONSTRAINED = -1; private static final int OPTIONS_NONE = 0x0; private static final int OPTIONS_SCALE_UP = 0x1; /** * Constant used to indicate we should recycle the input in * {@link #extractThumbnail(Bitmap, int, int, int)} unless the output is the input. */ public static final int OPTIONS_RECYCLE_INPUT = 0x2; /** * Constant used to indicate the dimension of mini thumbnail. * @hide Only used by media framework and media provider internally. */ public static final int TARGET_SIZE_MINI_THUMBNAIL = 320; /** * Constant used to indicate the dimension of micro thumbnail. * @hide Only used by media framework and media provider internally. */ public static final int TARGET_SIZE_MICRO_THUMBNAIL = 96; /** * This method first examines if the thumbnail embedded in EXIF is bigger than our target * size. If not, then it'll create a thumbnail from original image. Due to efficiency * consideration, we want to let MediaThumbRequest avoid calling this method twice for * both kinds, so it only requests for MICRO_KIND and set saveImage to true. * * This method always returns a "square thumbnail" for MICRO_KIND thumbnail. * * @param filePath the path of image file * @param kind could be MINI_KIND or MICRO_KIND * @return Bitmap * * @hide This method is only used by media framework and media provider internally. */ public static Bitmap createImageThumbnail(String filePath, int kind) { boolean wantMini = (kind == Images.Thumbnails.MINI_KIND); int targetSize = wantMini ? TARGET_SIZE_MINI_THUMBNAIL : TARGET_SIZE_MICRO_THUMBNAIL; int maxPixels = wantMini ? MAX_NUM_PIXELS_THUMBNAIL : MAX_NUM_PIXELS_MICRO_THUMBNAIL; // SizedThumbnailBitmap sizedThumbnailBitmap = new SizedThumbnailBitmap(); Bitmap bitmap = null; // MediaFileType fileType = ImageFile.getFileType(filePath); // if (fileType != null && fileType.fileType == ImageFile.FILE_TYPE_JPEG) // { // createThumbnailFromEXIF(filePath, targetSize, maxPixels, sizedThumbnailBitmap); // bitmap = sizedThumbnailBitmap.mBitmap; // } if (bitmap == null) { try { FileDescriptor fd = new FileInputStream(filePath).getFD(); BitmapFactory.Options options = new BitmapFactory.Options(); options.inSampleSize = 1; options.inJustDecodeBounds = true; BitmapFactory.decodeFileDescriptor(fd, null, options); if (options.mCancel || options.outWidth == -1 || options.outHeight == -1) { return null; } options.inSampleSize = computeSampleSize(options, targetSize, maxPixels); options.inJustDecodeBounds = false; options.inDither = false; options.inPreferredConfig = Bitmap.Config.ARGB_8888; bitmap = BitmapFactory.decodeFileDescriptor(fd, null, options); } catch (IOException ex) { Log.e(TAG, ex.getMessage()); } } if (kind == Images.Thumbnails.MICRO_KIND) { // now we make it a "square thumbnail" for MICRO_KIND thumbnail bitmap = extractThumbnail(bitmap, TARGET_SIZE_MICRO_THUMBNAIL, TARGET_SIZE_MICRO_THUMBNAIL, OPTIONS_RECYCLE_INPUT); } return bitmap; } private static int computeSampleSize(BitmapFactory.Options options, int minSideLength, int maxNumOfPixels) { int initialSize = computeInitialSampleSize(options, minSideLength, maxNumOfPixels); int roundedSize; if (initialSize <= 8) { roundedSize = 1; while (roundedSize < initialSize) { roundedSize <<= 1; } } else { roundedSize = (initialSize + 7) / 8 * 8; } return roundedSize; } /** * Creates a centered bitmap of the desired size. * * @param source original bitmap source * @param width targeted width * @param height targeted height */ public static Bitmap extractThumbnail(Bitmap source, int width, int height) { return extractThumbnail(source, width, height, OPTIONS_NONE); } /** * Creates a centered bitmap of the desired size. * * @param source original bitmap source * @param width targeted width * @param height targeted height * @param options options used during thumbnail extraction */ public static Bitmap extractThumbnail(Bitmap source, int width, int height, int options) { if (source == null) { return null; } float scale; if (source.getWidth() < source.getHeight()) { scale = width / (float) source.getWidth(); } else { scale = height / (float) source.getHeight(); } Matrix matrix = new Matrix(); matrix.setScale(scale, scale); Bitmap thumbnail = transform(matrix, source, width, height, OPTIONS_SCALE_UP | options); return thumbnail; } private static int computeInitialSampleSize(BitmapFactory.Options options, int minSideLength, int maxNumOfPixels) { double w = options.outWidth; double h = options.outHeight; int lowerBound = (maxNumOfPixels == UNCONSTRAINED) ? 1 : (int) Math.ceil(Math.sqrt(w * h / maxNumOfPixels)); int upperBound = (minSideLength == UNCONSTRAINED) ? 128 : (int) Math.min(Math.floor(w / minSideLength), Math.floor(h / minSideLength)); if (upperBound < lowerBound) { // return the larger one when there is no overlapping zone. return lowerBound; } if ((maxNumOfPixels == UNCONSTRAINED) && (minSideLength == UNCONSTRAINED)) { return 1; } else if (minSideLength == UNCONSTRAINED) { return lowerBound; } else { return upperBound; } } /** * Transform source Bitmap to targeted width and height. */ private static Bitmap transform(Matrix scaler, Bitmap source, int targetWidth, int targetHeight, int options) { boolean scaleUp = (options & OPTIONS_SCALE_UP) != 0; boolean recycle = (options & OPTIONS_RECYCLE_INPUT) != 0; int deltaX = source.getWidth() - targetWidth; int deltaY = source.getHeight() - targetHeight; if (!scaleUp && (deltaX < 0 || deltaY < 0)) { /* * In this case the bitmap is smaller, at least in one dimension, * than the target. Transform it by placing as much of the image * as possible into the target and leaving the top/bottom or * left/right (or both) black. */ Bitmap b2 = Bitmap.createBitmap(targetWidth, targetHeight, Bitmap.Config.ARGB_8888); Canvas c = new Canvas(b2); int deltaXHalf = Math.max(0, deltaX / 2); int deltaYHalf = Math.max(0, deltaY / 2); Rect src = new Rect(deltaXHalf, deltaYHalf, deltaXHalf + Math.min(targetWidth, source.getWidth()), deltaYHalf + Math.min(targetHeight, source.getHeight())); int dstX = (targetWidth - src.width()) / 2; int dstY = (targetHeight - src.height()) / 2; Rect dst = new Rect(dstX, dstY, targetWidth - dstX, targetHeight - dstY); c.drawBitmap(source, src, dst, null); if (recycle) { source.recycle(); } return b2; } float bitmapWidthF = source.getWidth(); float bitmapHeightF = source.getHeight(); float bitmapAspect = bitmapWidthF / bitmapHeightF; float viewAspect = (float) targetWidth / targetHeight; if (bitmapAspect > viewAspect) { float scale = targetHeight / bitmapHeightF; if (scale < .9F || scale > 1F) { scaler.setScale(scale, scale); } else { scaler = null; } } else { float scale = targetWidth / bitmapWidthF; if (scale < .9F || scale > 1F) { scaler.setScale(scale, scale); } else { scaler = null; } } Bitmap b1; if (scaler != null) { // this is used for minithumb and crop, so we want to filter here. b1 = Bitmap.createBitmap(source, 0, 0, source.getWidth(), source.getHeight(), scaler, true); } else { b1 = source; } if (recycle && b1 != source) { source.recycle(); } int dx1 = Math.max(0, b1.getWidth() - targetWidth); int dy1 = Math.max(0, b1.getHeight() - targetHeight); Bitmap b2 = Bitmap.createBitmap(b1, dx1 / 2, dy1 / 2, targetWidth, targetHeight); if (b2 != b1) { if (recycle || b1 != source) { b1.recycle(); } } return b2; } }