前言：借鉴了几篇大牛的文章，整合了一个图片工具类，主要功能集中在'"保存“、“压缩”上。
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；
尺寸压缩一般可用于生成缩略图。
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bitmap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；
/**
* @desc
* @auth 方毅超
* @time 2017/11/1 8:59
*/
public class ImageUtil {
private ImageUtil() {
/* cannot be instantiated */
throw new UnsupportedOperationException("cannot be instantiated");
}
/**
* Get bitmap from specified image path
*
* @param imgPath
* @return
*/
public static Bitmap getBitmap(String imgPath) {
// Get bitmap through image path
BitmapFactory.Options newOpts = new BitmapFactory.Options();
// 防止OOM发生
newOpts.inJustDecodeBounds = false;
// Do not compress
newOpts.inSampleSize = 1;
newOpts.inPreferredConfig = Bitmap.Config.RGB_565;
return BitmapFactory.decodeFile(imgPath, newOpts);
}
/**
* Store bitmap into specified image path
*
* @param bitmap
* @param outPath
* @throws FileNotFoundException
*/
public static void storeImage(Bitmap bitmap, String outPath) throws FileNotFoundException {
FileOutputStream os = new FileOutputStream(outPath);
bitmap.compress(Bitmap.CompressFormat.JPEG, 100, os);
//??为什么不用flush？？
}
/**
* 保存图片至本地、插入到系统图库、通知图库更新
*
* @param context
* @param bmp
* @return
*/
public static boolean saveImageToGallery(Context context, Bitmap bmp) {
// 首先保存图片
File appDir = new File(Environment.getExternalStorageDirectory(), "Csair");
if (!appDir.exists()) {
appDir.mkdir();
}
String fileName = System.currentTimeMillis() + ".jpg";
File file = new File(appDir, fileName);
try {
FileOutputStream fos = new FileOutputStream(file);
bmp.compress(Bitmap.CompressFormat.JPEG, 100, fos);
fos.flush();
fos.close();
} catch (IOException e) {
e.printStackTrace();
return false;
}
// 其次把文件插入到系统图库
try {
MediaStore.Images.Media.insertImage(context.getContentResolver(),
file.getAbsolutePath(), fileName, null);
} catch (FileNotFoundException e) {
e.printStackTrace();
return false;
}
// 通知图库更新
/** MediaScanner 扫描更新图库图片 **/
// MediaScannerConnection.scanFile(context, new String[]{file.getAbsolutePath()}, null, null);
// 最后通知图库更新
/** Receiver扫描更新图库图片，各种型号版本机子都没问题 **/
context.sendBroadcast(new Intent(Intent.ACTION_MEDIA_SCANNER_SCAN_FILE, Uri.fromFile(file)));
return true;
}
/**
* 尺寸压缩
* 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 static 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 = Bitmap.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高度固定大小缩放
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;
}
/**
* 尺寸压缩
* 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 static 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 = Bitmap.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;
}
/**
* 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 static 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 imgPath
* @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 static 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 file
if (needsDelete) {
File file = new File(imgPath);
if (file.exists()) {
file.delete();
}
}
}
/**
* 质量压缩方法
*
* @param bitmap
* @param maxSize 100k
* @return
*/
public static Bitmap compressImage(Bitmap bitmap, int maxSize) {
ByteArrayOutputStream baos = new ByteArrayOutputStream();
// scale
int options = 100;
// Store the bitmap into output stream(no compress)
bitmap.compress(Bitmap.CompressFormat.JPEG, options, baos);
// Compress by loop
while (baos.toByteArray().length / 1024 > maxSize) {
// Clean up os
baos.reset();
// interval 10
options -= 10;
bitmap.compress(Bitmap.CompressFormat.JPEG, options, baos);
}
ByteArrayInputStream isBm = new ByteArrayInputStream(baos.toByteArray());// 把压缩后的数据baos存放到ByteArrayInputStream中
return BitmapFactory.decodeStream(isBm, null, null);// 把ByteArrayInputStream数据生成图片
}
/**
* @param imgPath
* @param maxSize 100k
* @return
*/
public static Bitmap compressImage(String imgPath, int maxSize) {
return compressImage(getBitmap(imgPath), maxSize);
}
/**
* 质量压缩
* Compress by quality, and generate image to the path specified
*
* @param bitmap
* @param outPath
* @param maxSize target will be compressed to be smaller than this size.(kb)
* @throws IOException
*/
public static void compressAndGenImage(Bitmap bitmap, String outPath, int maxSize) throws IOException {
ByteArrayOutputStream os = new ByteArrayOutputStream();
// scale
int options = 100;
// Store the bitmap into output stream(no compress)
bitmap.compress(Bitmap.CompressFormat.JPEG, options, os);
// Compress by loop
while (os.toByteArray().length / 1024 > maxSize) {
// Clean up os
os.reset();
// interval 10
options -= 10;
bitmap.compress(Bitmap.CompressFormat.JPEG, options, os);
}
// Generate compressed image file
FileOutputStream fos = new FileOutputStream(outPath);
fos.write(os.toByteArray());
fos.flush();
fos.close();
}
/**
* 质量压缩
* 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 static void compressAndGenImage(String imgPath, String outPath, int maxSize, boolean needsDelete) throws IOException {
compressAndGenImage(getBitmap(imgPath), outPath, maxSize);
// Delete original file
if (needsDelete) {
File file = new File(imgPath);
if (file.exists()) {
file.delete();
}
}
}
/**
* 图片转成string
*
* @param bitmap
* @return
*/
public static String convertIconToString(Bitmap bitmap) {
ByteArrayOutputStream baos = new ByteArrayOutputStream();// outputstream
bitmap.compress(Bitmap.CompressFormat.PNG, 100, baos);
byte[] appicon = baos.toByteArray();// 转为byte数组
return Base64.encodeToString(appicon, Base64.DEFAULT);
}
/**
* string转成bitmap
*
* @param st
*/
public static Bitmap convertStringToIcon(String st) {
// OutputStream out;
Bitmap bitmap = null;
try {
// out = new FileOutputStream("/sdcard/aa.jpg");
byte[] bitmapArray;
bitmapArray = Base64.decode(st, Base64.DEFAULT);
bitmap = BitmapFactory.decodeByteArray(bitmapArray, 0,
bitmapArray.length);
// bitmap.compress(Bitmap.CompressFormat.PNG, 100, out);
return bitmap;
} catch (Exception e) {
return null;
}
}
/**
* 图片文件转换为指定编码的字符串
*
* @param imgFile 图片文件
*/
public static String convertFileToString(File imgFile) {
InputStream in = null;
byte[] data = null;
//读取图片字节数组
try {
in = new FileInputStream(imgFile);
data = new byte[in.available()];
in.read(data);
in.close();
} catch (IOException e) {
e.printStackTrace();
}
//对字节数组Base64编码
// BASE64Encoder encoder = new BASE64Encoder();//fangyc,找不到BASE64Encoder
// String result = encoder.encode(data);
String result = Base64.encodeToString(data, Base64.DEFAULT);//fangyc 该句未得到实机验证
return result;//返回Base64编码过的字节数组字符串
}
}
感谢：
Android图片压缩（质量压缩和尺寸压缩）&Bitmap转成字符串上传
Android图片压缩实现过程及代码
ANDROID保存图片到系统图库