Android图片压缩（质量压缩和尺寸压缩）

在网上调查了图片压缩的方法并实装后，大致上可以认为有两类压缩：质量压缩（不改变图片的尺寸）和尺寸压缩（相当于是像素上的压缩）；质量压缩一般可用于上传大图前的处理，这样就可以节省一定的流量，毕竟现在的手机拍照都能达到3M左右了，尺寸压缩一般可用于生成缩略图。
两种方法都实装在了我的项目中，结果却发现在质量压缩的模块中，本来1.9M的图片压缩后反而变成3M多了，很是奇怪，再做了进一步调查终于知道原因了。下面这个博客说的比较清晰：

android图片压缩总结

总结来看，图片有三种存在形式：硬盘上时是file，网络传输时是stream，内存中是stream或bitmap，所谓的质量压缩，它其实只能实现对file的影响，你可以把一个file转成bitmap再转成file，或者直接将一个bitmap转成file时，这个最终的file是被压缩过的，但是中间的bitmap并没有被压缩（或者说几乎没有被压缩，我不确定），因为bigmap在内存中的大小是按像素计算的，也就是width * height，对于质量压缩，并不会改变图片的像素，所以就算质量被压缩了，但是bitmap在内存的占有率还是没变小，但你做成file时，它确实变小了；

而尺寸压缩由于是减小了图片的像素，所以它直接对bitmap产生了影响，当然最终的file也是相对的变小了；

最后把自己总结的工具类贴出来：

import java.io.ByteArrayInputStream;import java.io.ByteArrayOutputStream;import java.io.File;import java.io.FileNotFoundException;import java.io.FileOutputStream;import java.io.IOException;import android.graphics.Bitmap;import android.graphics.Bitmap.Config;import android.graphics.BitmapFactory;/** * Image compress factory class *  * @author  * */public class ImageFactory {/** * Get bitmap from specified image path *  * @param imgPath * @return */public Bitmap getBitmap(String imgPath) {// Get bitmap through image pathBitmapFactory.Options newOpts = new BitmapFactory.Options();newOpts.inJustDecodeBounds = false;newOpts.inPurgeable = true;newOpts.inInputShareable = true;// Do not compressnewOpts.inSampleSize = 1;newOpts.inPreferredConfig = Config.RGB_565;return BitmapFactory.decodeFile(imgPath, newOpts);}/** * Store bitmap into specified image path *  * @param bitmap * @param outPath * @throws FileNotFoundException  */public void storeImage(Bitmap bitmap, String outPath) throws FileNotFoundException {FileOutputStream os = new FileOutputStream(outPath);bitmap.compress(Bitmap.CompressFormat.JPEG, 100, os);}/** * Compress image by pixel, this will modify image width/height.  * Used to get thumbnail *  * @param imgPath image path * @param pixelW target pixel of width * @param pixelH target pixel of height * @return */public Bitmap ratio(String imgPath, float pixelW, float pixelH) {BitmapFactory.Options newOpts = new BitmapFactory.Options();          // 开始读入图片，此时把options.inJustDecodeBounds 设回true，即只读边不读内容        newOpts.inJustDecodeBounds = true;        newOpts.inPreferredConfig = Config.RGB_565;        // Get bitmap info, but notice that bitmap is null now          Bitmap bitmap = BitmapFactory.decodeFile(imgPath,newOpts);                  newOpts.inJustDecodeBounds = false;          int w = newOpts.outWidth;          int h = newOpts.outHeight;          // 想要缩放的目标尺寸        float hh = pixelH;// 设置高度为240f时，可以明显看到图片缩小了    float ww = pixelW;// 设置宽度为120f，可以明显看到图片缩小了        // 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        // 开始压缩图片，注意此时已经把options.inJustDecodeBounds 设回false了        bitmap = BitmapFactory.decodeFile(imgPath, newOpts);        // 压缩好比例大小后再进行质量压缩//        return compress(bitmap, maxSize); // 这里再进行质量压缩的意义不大，反而耗资源，删除        return bitmap;}/** * Compress image by size, this will modify image width/height.  * Used to get thumbnail *  * @param image * @param pixelW target pixel of width * @param pixelH target pixel of height * @return */public Bitmap ratio(Bitmap image, float pixelW, float pixelH) {ByteArrayOutputStream os = new ByteArrayOutputStream();    image.compress(Bitmap.CompressFormat.JPEG, 100, os);    if( os.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            os.reset();//重置baos即清空baos          image.compress(Bitmap.CompressFormat.JPEG, 50, os);//这里压缩50%，把压缩后的数据存放到baos中      }      ByteArrayInputStream is = new ByteArrayInputStream(os.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;    newOpts.inPreferredConfig = Config.RGB_565;    Bitmap bitmap = BitmapFactory.decodeStream(is, null, newOpts);      newOpts.inJustDecodeBounds = false;      int w = newOpts.outWidth;      int h = newOpts.outHeight;      float hh = pixelH;// 设置高度为240f时，可以明显看到图片缩小了    float ww = pixelW;// 设置宽度为120f，可以明显看到图片缩小了    //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      is = new ByteArrayInputStream(os.toByteArray());      bitmap = BitmapFactory.decodeStream(is, null, newOpts);    //压缩好比例大小后再进行质量压缩//    return compress(bitmap, maxSize); // 这里再进行质量压缩的意义不大，反而耗资源，删除    return bitmap;}/** * Compress by quality,  and generate image to the path specified *  * @param image * @param outPath * @param maxSize target will be compressed to be smaller than this size.(kb) * @throws IOException  */public void compressAndGenImage(Bitmap image, String outPath, int maxSize) throws IOException {ByteArrayOutputStream os = new ByteArrayOutputStream();// scaleint options = 100;// Store the bitmap into output stream(no compress)        image.compress(Bitmap.CompressFormat.JPEG, options, os);          // Compress by loop        while ( os.toByteArray().length / 1024 > maxSize) {            // Clean up os        os.reset();        // interval 10            options -= 10;            image.compress(Bitmap.CompressFormat.JPEG, options, os);        }                // Generate compressed image file        FileOutputStream fos = new FileOutputStream(outPath);          fos.write(os.toByteArray());          fos.flush();          fos.close();  }/** * Compress by quality,  and generate image to the path specified *  * @param imgPath * @param outPath * @param maxSize target will be compressed to be smaller than this size.(kb) * @param needsDelete Whether delete original file after compress * @throws IOException  */public void compressAndGenImage(String imgPath, String outPath, int maxSize, boolean needsDelete) throws IOException {compressAndGenImage(getBitmap(imgPath), outPath, maxSize);// Delete original fileif (needsDelete) {File file = new File (imgPath);if (file.exists()) {file.delete();}}}/** * Ratio and generate thumb to the path specified *  * @param image * @param outPath * @param pixelW target pixel of width * @param pixelH target pixel of height * @throws FileNotFoundException */public void ratioAndGenThumb(Bitmap image, String outPath, float pixelW, float pixelH) throws FileNotFoundException {Bitmap bitmap = ratio(image, pixelW, pixelH);storeImage( bitmap, outPath);}/** * Ratio and generate thumb to the path specified *  * @param image * @param outPath * @param pixelW target pixel of width * @param pixelH target pixel of height * @param needsDelete Whether delete original file after compress * @throws FileNotFoundException */public void ratioAndGenThumb(String imgPath, String outPath, float pixelW, float pixelH, boolean needsDelete) throws FileNotFoundException {Bitmap bitmap = ratio(imgPath, pixelW, pixelH);storeImage( bitmap, outPath);// Delete original fileif (needsDelete) {File file = new File (imgPath);if (file.exists()) {file.delete();}}}}