Overview of the Android image compression method

This article summarizes three kinds of common image compression methods in Android application development, namely: mass compression method, proportional compression method (obtain picture according to path and compress) and proportional compression method (according to bitmap image compression).

First: Quality compression method:?

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private Bitmap compressImage(Bitmap image) {         ByteArrayOutputStream baos = new ByteArrayOutputStream();        image.compress(Bitmap.CompressFormat.JPEG, 100, baos);//质量压缩方法，这里100表示不压缩，把压缩后的数据存放到baos中        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();//重置baos即清空baos            image.compress(Bitmap.CompressFormat.JPEG, options, baos);//这里压缩options%，把压缩后的数据存放到baos中            options -= 10;//每次都减少10        }        ByteArrayInputStream isBm = new ByteArrayInputStream(baos.toByteArray());//把压缩后的数据baos存放到ByteArrayInputStream中        Bitmap bitmap = BitmapFactory.decodeStream(isBm, null, null);//把ByteArrayInputStream数据生成图片        return bitmap;    }

Second: Picture by proportional size compression method (get picture according to Path and compress):

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private Bitmap getimage(String srcPath) {        BitmapFactory.Options newOpts = new BitmapFactory.Options();        //开始读入图片，此时把options.inJustDecodeBounds 设回true了        newOpts.inJustDecodeBounds = true;        Bitmap bitmap = BitmapFactory.decodeFile(srcPath,newOpts);//此时返回bm为空                 newOpts.inJustDecodeBounds = false;        int w = newOpts.outWidth;        int h = newOpts.outHeight;        //现在主流手机比较多是800*480分辨率，所以高和宽我们设置为        float hh = 800f;//这里设置高度为800f        float ww = 480f;//这里设置宽度为480f        //缩放比。由于是固定比例缩放，只用高或者宽其中一个数据进行计算即可        int be = 1;//be=1表示不缩放        if (w > h && w > ww) {//如果宽度大的话根据宽度固定大小缩放            be = (int) (newOpts.outWidth / ww);        } else if (w < h && h > hh) {//如果高度高的话根据宽度固定大小缩放            be = (int) (newOpts.outHeight / hh);        }        if (be <= 0)            be = 1;        newOpts.inSampleSize = be;//设置缩放比例        //重新读入图片，注意此时已经把options.inJustDecodeBounds 设回false了        bitmap = BitmapFactory.decodeFile(srcPath, newOpts);        return compressImage(bitmap);//压缩好比例大小后再进行质量压缩    }

Third: Image compression by proportional size (according to bitmap image compression):

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private Bitmap comp(Bitmap image) {         ByteArrayOutputStream baos = new ByteArrayOutputStream();    image.compress(Bitmap.CompressFormat.JPEG, 100, baos);    if( baos.toByteArray().length / 1024>1024) {//判断如果图片大于1M,进行压缩避免在生成图片（BitmapFactory.decodeStream）时溢出        baos.reset();//重置baos即清空baos        image.compress(Bitmap.CompressFormat.JPEG, 50, baos);//这里压缩50%，把压缩后的数据存放到baos中    }    ByteArrayInputStream isBm = new ByteArrayInputStream(baos.toByteArray());    BitmapFactory.Options newOpts = new BitmapFactory.Options();    //开始读入图片，此时把options.inJustDecodeBounds 设回true了    newOpts.inJustDecodeBounds = true;    Bitmap bitmap = BitmapFactory.decodeStream(isBm, null, newOpts);    newOpts.inJustDecodeBounds = false;    int w = newOpts.outWidth;    int h = newOpts.outHeight;    //现在主流手机比较多是800*480分辨率，所以高和宽我们设置为    float hh = 800f;//这里设置高度为800f    float ww = 480f;//这里设置宽度为480f    //缩放比。由于是固定比例缩放，只用高或者宽其中一个数据进行计算即可    int be = 1;//be=1表示不缩放    if (w > h && w > ww) {//如果宽度大的话根据宽度固定大小缩放        be = (int) (newOpts.outWidth / ww);    } else if (w < h && h > hh) {//如果高度高的话根据宽度固定大小缩放        be = (int) (newOpts.outHeight / hh);    }    if (be <= 0)        be = 1;    newOpts.inSampleSize = be;//设置缩放比例    //重新读入图片，注意此时已经把options.inJustDecodeBounds 设回false了    isBm = new ByteArrayInputStream(baos.toByteArray());    bitmap = BitmapFactory.decodeStream(isBm, null, newOpts);    return compressImage(bitmap);//压缩好比例大小后再进行质量压缩}

Overview of the Android image compression method