android bitmap compress(图片压缩)代码

程序员文章站 2023-11-12 10:08:40

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...

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：

1. 照相请查看 ->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]

复制代码代码如下:

final bitmapfactory.options options = new bitmapfactory.options();
    options.injustdecodebounds = true;
    bitmapfactory.decodefile(filepath, options);

    // calculate insamplesize
    options.insamplesize = calculateinsamplesize(options, 480, 800);

    // decode bitmap with insamplesize set
    options.injustdecodebounds = false;

    bitmap bm = bitmapfactory.decodefile(filepath, options);

final bitmapfactory.options options = new bitmapfactory.options();
options.injustdecodebounds = true;
bitmapfactory.decodefile(filepath, options);

// calculate insamplesize
options.insamplesize = calculateinsamplesize(options, 480, 800);

// decode bitmap with insamplesize set
options.injustdecodebounds = false;

bitmap bm = bitmapfactory.decodefile(filepath, options);

2.2 处理图片旋转
[java]

复制代码代码如下:

int degree = readpicturedegree(filepath);
bm = rotatebitmap(bm,degree) ;

int degree = readpicturedegree(filepath);
bm = rotatebitmap(bm,degree) ;[java] view plaincopyprint?private static int readpicturedegree(string path) {
           int degree = 0;
           try {
                   exifinterface exifinterface = new exifinterface(path);
                   int orientation = exifinterface.getattributeint(exifinterface.tag_orientation, exifinterface.orientation_normal);
                   switch (orientation) {
                   case exifinterface.orientation_rotate_90:
                           degree = 90;
                           break;
                   case exifinterface.orientation_rotate_180:
                           degree = 180;
                           break;
                   case exifinterface.orientation_rotate_270:
                           degree = 270;
                           break;
                   }
           } catch (ioexception e) {
                   e.printstacktrace();
           }
           return degree;
       }

private static int readpicturedegree(string path) {
        int degree = 0;
        try {
                exifinterface exifinterface = new exifinterface(path);
                int orientation = exifinterface.getattributeint(exifinterface.tag_orientation, exifinterface.orientation_normal);
                switch (orientation) {
                case exifinterface.orientation_rotate_90:
                        degree = 90;
                        break;
                case exifinterface.orientation_rotate_180:
                        degree = 180;
                        break;
                case exifinterface.orientation_rotate_270:
                        degree = 270;
                        break;
                }
        } catch (ioexception e) {
                e.printstacktrace();
        }
        return degree;
    }

[java]

复制代码代码如下:

view plaincopyprint?private static bitmap rotatebitmap(bitmap bitmap, int rotate){
        if(bitmap == null)
            return null ;

        int w = bitmap.getwidth();
        int h = bitmap.getheight();

        // setting post rotate to 90
        matrix mtx = new matrix();
        mtx.postrotate(rotate);
        return bitmap.createbitmap(bitmap, 0, 0, w, h, mtx, true);
    }

private static bitmap rotatebitmap(bitmap bitmap, int rotate){
if(bitmap == null)
return null ;

int w = bitmap.getwidth();
int h = bitmap.getheight();

// setting post rotate to 90
matrix mtx = new matrix();
mtx.postrotate(rotate);
return bitmap.createbitmap(bitmap, 0, 0, w, h, mtx, true);
}

2.3压缩图片
[java]

复制代码代码如下:

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]

复制代码代码如下:

public static bitmap getsmallbitmap(string filepath) {

        final bitmapfactory.options options = new bitmapfactory.options();
        options.injustdecodebounds = true;
        bitmapfactory.decodefile(filepath, options);

        // calculate insamplesize
        options.insamplesize = calculateinsamplesize(options, 480, 800);

        // decode bitmap with insamplesize set
        options.injustdecodebounds = false;

        bitmap bm = bitmapfactory.decodefile(filepath, options);
        if(bm == null){
            return null;
        }
        int degree = readpicturedegree(filepath);
        bm = rotatebitmap(bm,degree) ;
        bytearrayoutputstream baos = null ;
        try{
            baos = new bytearrayoutputstream();
            bm.compress(bitmap.compressformat.jpeg, 30, baos);

        }finally{
            try {
                if(baos != null)
                    baos.close() ;
            } catch (ioexception e) {
                e.printstacktrace();
            }
        }
        return bm ;

    }

// calculate insamplesize
options.insamplesize = calculateinsamplesize(options, 480, 800);

// decode bitmap with insamplesize set
options.injustdecodebounds = false;

bitmap bm = bitmapfactory.decodefile(filepath, options);
if(bm == null){
   return null;
}
int degree = readpicturedegree(filepath);
bm = rotatebitmap(bm,degree) ;
bytearrayoutputstream baos = null ;
try{
   baos = new bytearrayoutputstream();
   bm.compress(bitmap.compressformat.jpeg, 30, baos);

}finally{
   try {
    if(baos != null)
     baos.close() ;
   } catch (ioexception e) {
    e.printstacktrace();
   }
}
return bm ;

}

[java]

复制代码代码如下:

view plaincopyprint?private static int calculateinsamplesize(bitmapfactory.options options,
            int reqwidth, int reqheight) {
        // raw height and width of image
        final int height = options.outheight;
        final int width = options.outwidth;
        int insamplesize = 1;

        if (height > reqheight || width > reqwidth) {

            // calculate ratios of height and width to requested height and
            // width
            final int heightratio = math.round((float) height
                    / (float) reqheight);
            final int widthratio = math.round((float) width / (float) reqwidth);

            // choose the smallest ratio as insamplesize value, this will
            // guarantee
            // a final image with both dimensions larger than or equal to the
            // requested height and width.
            insamplesize = heightratio < widthratio ? widthratio : heightratio;
        }

        return insamplesize;
    }

private static int calculateinsamplesize(bitmapfactory.options options,
int reqwidth, int reqheight) {
// raw height and width of image
final int height = options.outheight;
final int width = options.outwidth;
int insamplesize = 1;

if (height > reqheight || width > reqwidth) {

   // calculate ratios of height and width to requested height and
   // width
   final int heightratio = math.round((float) height
     / (float) reqheight);
   final int widthratio = math.round((float) width / (float) reqwidth);

   // choose the smallest ratio as insamplesize value, this will
   // guarantee
   // a final image with both dimensions larger than or equal to the
   // requested height and width.
   insamplesize = heightratio < widthratio ? widthratio : heightratio;
}

return insamplesize;
}

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