android 图片压缩

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图片压缩常用的两种方式：

质量压缩
按比例压缩

1、质量压缩

    /**     * 质量压缩     */    public static Bitmap compressImage(Bitmap bitmap) {        ByteArrayOutputStream baos = new ByteArrayOutputStream();        bitmap.compress(Bitmap.CompressFormat.JPEG, 100, baos);        int options = 100;        while (baos.toByteArray().length / 1024 > 100) { //循环判断如果压缩后图片是否大于100kb,大于继续压缩            baos.reset();//清空baos            options -= 10;            bitmap.compress(Bitmap.CompressFormat.JPEG, options, baos);        }        ByteArrayInputStream bais = new ByteArrayInputStream(baos.toByteArray());        Bitmap compressBitmap = BitmapFactory.decodeStream(bais);        return compressBitmap;    }

按比例压缩

先要读取位图的尺寸与类型

        BitmapFactory.Options options = new BitmapFactory.Options();        //在解码的时候，避免内存的分配，即它会返回一个null的Bitmap对象        //但是可以获取它的尺寸与类型,outWidth,outHeight与outMineType        options.inJustDecodeBounds = true;        BitmapFactory.decodeResource(getResources(), R.drawable.picture,options);        int imageWidth = options.outWidth;        int imageHeight = options.outHeight;        String imageType = options.outMimeType;

计算inSampleSize的值

        public static int calculateInSampleSize(            BitmapFactory.Options options, int reqWidth, int reqHeight) {        //原始图片的宽和高        final int height = options.outHeight;        final int width = options.outWidth;        int inSampleSize = 1;        if (height > reqHeight || width > reqWidth) {            final int halfHeight = height / 2;            final int halfWidth = width / 2;            while ((halfHeight / inSampleSize) > reqHeight &&                    (halfWidth / inSampleSize) > reqWidth) {                inSampleSize *= 2;            }        }        return inSampleSize;    }

获取压缩后的图片

        public static Bitmap decodeSampleBitmapFromResource(            Resources res, int resId, int reqWidth, int reqHeight) {        BitmapFactory.Options options = new BitmapFactory.Options();        options.inJustDecodeBounds = true;        BitmapFactory.decodeResource(res, resId, options);        options.inSampleSize = calculateInSampleSize(options, reqWidth, reqWidth);        options.inJustDecodeBounds = false;        return BitmapFactory.decodeResource(res, resId, options);    }

最后直接可以显示了

mImg.setImageBitmap(    decodeSampledBitmapFromResource(getResources(), R.id.picture, 100, 100));

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