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android bit地图 compress（图片压缩）

热度：165   发布时间：2016-04-27 23:20:37.0
android bitmap compress（图片压缩）

转自：http://blog.csdn.net/luhuajcdd/article/details/8948261

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android bitmap compress

android的照相功能随着手机硬件的发展，变得越来越强大，能够找出很高分辨率的图片。
有些场景中，需要照相并且上传到服务，但是由于图片的大小太大，那么就上传就会很慢(在有些网络情况下)，而且很耗流量，要想速度快，那么就需要减小图片的大小。减少图片的大小有两种方法，1. 照小图片； 2. 压缩大图片。 照相时获取小图片一般不太符合要求，因为，图片的清晰度会很差，但是这种情况有个好处就是应用速度会快些； 压缩图片，就是把大图片压缩小，降低图片的质量，在一定范围内，降低图片的大小，并且满足需求（图片仍就清晰）。下面组要是介绍图片的压缩：
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1. 照相请查看http://blog.csdn.net/luhuajcdd/article/details/8826587?->想要保存图片到制定目录，启动Camera应用时，需要指定文件
2. 压缩过程：
? ? 2.1 从图片路径中读取图片(图片很大，不能全部加在到内存中处理，要是全部加载到内存中会内存溢出)
[java]?view plaincopy
?
  1. final?BitmapFactory.Options?options?=?new?BitmapFactory.Options();??
  2. ????options.inJustDecodeBounds?=?true;??
  3. ????BitmapFactory.decodeFile(filePath,?options);??
  4. ??
  5. ????//?Calculate?inSampleSize??
  6. ????options.inSampleSize?=?calculateInSampleSize(options,?480,?800);??
  7. ??
  8. ????//?Decode?bitmap?with?inSampleSize?set??
  9. ????options.inJustDecodeBounds?=?false;??
  10. ??????
  11. ????Bitmap?bm?=?BitmapFactory.decodeFile(filePath,?options);??
? ? 2.2 处理图片旋转? ?
[java]?view plaincopy
?
  1. int?degree?=?readPictureDegree(filePath);??
  2. ????????bm?=?rotateBitmap(bm,degree)?;??
[java]?view plaincopy
?
  1. private?static?int?readPictureDegree(String?path)?{????
  2. ???????????int?degree??=?0;????
  3. ???????????try?{????
  4. ???????????????????ExifInterface?exifInterface?=?new?ExifInterface(path);????
  5. ???????????????????int?orientation?=?exifInterface.getAttributeInt(ExifInterface.TAG_ORIENTATION,?ExifInterface.ORIENTATION_NORMAL);????
  6. ???????????????????switch?(orientation)?{????
  7. ???????????????????case?ExifInterface.ORIENTATION_ROTATE_90:????
  8. ???????????????????????????degree?=?90;????
  9. ???????????????????????????break;????
  10. ???????????????????case?ExifInterface.ORIENTATION_ROTATE_180:????
  11. ???????????????????????????degree?=?180;????
  12. ???????????????????????????break;????
  13. ???????????????????case?ExifInterface.ORIENTATION_ROTATE_270:????
  14. ???????????????????????????degree?=?270;????
  15. ???????????????????????????break;????
  16. ???????????????????}????
  17. ???????????}?catch?(IOException?e)?{????
  18. ???????????????????e.printStackTrace();????
  19. ???????????}????
  20. ???????????return?degree;????
  21. ???????}???
[java]?view plaincopy
?
  1. private?static?Bitmap?rotateBitmap(Bitmap?bitmap,?int?rotate){??
  2. ????????if(bitmap?==?null)??
  3. ????????????return?null?;??
  4. ??????????
  5. ????????int?w?=?bitmap.getWidth();??
  6. ????????int?h?=?bitmap.getHeight();??
  7. ??
  8. ????????//?Setting?post?rotate?to?90??
  9. ????????Matrix?mtx?=?new?Matrix();??
  10. ????????mtx.postRotate(rotate);??
  11. ????????return?Bitmap.createBitmap(bitmap,?0,?0,?w,?h,?mtx,?true);??
  12. ????}??
? ? 2.3压缩图片? ? ? ??
[java]?view plaincopy
?
  1. bm.compress(Bitmap.CompressFormat.JPEG,?30,?baos);//30?是压缩率，表示压缩70%;?如果不压缩是100，表示压缩率为0??
?
完整的方法代码：
[java]?view plaincopy
?
  1. public?static?Bitmap?getSmallBitmap(String?filePath)?{??
  2. ??????????????
  3. ????????final?BitmapFactory.Options?options?=?new?BitmapFactory.Options();??
  4. ????????options.inJustDecodeBounds?=?true;??
  5. ????????BitmapFactory.decodeFile(filePath,?options);??
  6. ??
  7. ????????//?Calculate?inSampleSize??
  8. ????????options.inSampleSize?=?calculateInSampleSize(options,?480,?800);??
  9. ??
  10. ????????//?Decode?bitmap?with?inSampleSize?set??
  11. ????????options.inJustDecodeBounds?=?false;??
  12. ??????????
  13. ????????Bitmap?bm?=?BitmapFactory.decodeFile(filePath,?options);??
  14. ????????if(bm?==?null){??
  15. ????????????return??null;??
  16. ????????}??
  17. ????????int?degree?=?readPictureDegree(filePath);??
  18. ????????bm?=?rotateBitmap(bm,degree)?;??
  19. ????????ByteArrayOutputStream?baos?=?null?;??
  20. ????????try{??
  21. ????????????baos?=?new?ByteArrayOutputStream();??
  22. ????????????bm.compress(Bitmap.CompressFormat.JPEG,?30,?baos);??
  23. ??????????????
  24. ????????}finally{??
  25. ????????????try?{??
  26. ????????????????if(baos?!=?null)??
  27. ????????????????????baos.close()?;??
  28. ????????????}?catch?(IOException?e)?{??
  29. ????????????????e.printStackTrace();??
  30. ????????????}??
  31. ????????}??
  32. ????????return?bm?;??
  33. ??
  34. ????}??
[java]?view plaincopy
?
  1. private?static?int?calculateInSampleSize(BitmapFactory.Options?options,??
  2. ????????????int?reqWidth,?int?reqHeight)?{??
  3. ????????//?Raw?height?and?width?of?image??
  4. ????????final?int?height?=?options.outHeight;??
  5. ????????final?int?width?=?options.outWidth;??
  6. ????????int?inSampleSize?=?1;??
  7. ??
  8. ????????if?(height?>?reqHeight?||?width?>?reqWidth)?{??
  9. ??
  10. ????????????//?Calculate?ratios?of?height?and?width?to?requested?height?and??
  11. ????????????//?width??
  12. ????????????final?int?heightRatio?=?Math.round((float)?height??
  13. ????????????????????/?(float)?reqHeight);??
  14. ????????????final?int?widthRatio?=?Math.round((float)?width?/?(float)?reqWidth);??
  15. ??
  16. ????????????//?Choose?the?smallest?ratio?as?inSampleSize?value,?this?will??
  17. ????????????//?guarantee??
  18. ????????????//?a?final?image?with?both?dimensions?larger?than?or?equal?to?the??
  19. ????????????//?requested?height?and?width.??
  20. ????????????inSampleSize?=?heightRatio?<?widthRatio???widthRatio?:?heightRatio;??
  21. ????????}??
  22. ??
  23. ????????return?inSampleSize;??
  24. ????}??
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