Android图片压缩几种方式总结

android图片压缩几种方式总结

图片压缩在android开发中很常见也很重要，防止图片的oom也是压缩的重要原因。

首先看下bitmap图片文件的大小的决定因素：

bitmap所占用的内存 = 图片长度 x 图片宽度 x 一个像素点占用的字节数。3个参数，任意减少一个的值，就达到了压缩的效果。

接下来看下bitmap图片的几种格式的特点：

alpha_8
 表示8位alpha位图,即a=8,一个像素点占用1个字节,它没有颜色,只有透明度
 argb_4444
表示16位argb位图，即a=4,r=4,g=4,b=4,一个像素点占4+4+4+4=16位，2个字节
argb_8888
表示32位argb位图，即a=8,r=8,g=8,b=8,一个像素点占8+8+8+8=32位，4个字节
rgb_565
表示16位rgb位图,即r=5,g=6,b=5,它没有透明度,一个像素点占5+6+5=16位，2个字节

如果进行图片格式的压缩的话，一般情况下都是argb_8888转为rgb565进行压缩。

写了一个工具类，基本上列举了android上图片的几种基本压缩方式：

1.质量压缩

2.采样率压缩

3.尺寸压缩

4.matrix压缩

5.图片格式的压缩，例如png和jpg保存后的图片大小是不同的

public class utils { 
 
  /** 
   * 采样率压缩 
   * 
   * @param bitmap 
   * @param samplesize 采样率为2的整数倍，非整数倍四舍五入，如4的话，就是原图的1/4 
   * @return 尺寸变化 
   */ 
  public static bitmap getbitmap(bitmap bitmap, int samplesize) { 
    bitmapfactory.options options = new bitmapfactory.options(); 
    options.insamplesize = samplesize; 
    bytearrayoutputstream baos = new bytearrayoutputstream(); 
    bitmap.compress(bitmap.compressformat.jpeg, 100, baos); 
    byte[] bytes = baos.tobytearray(); 
    bitmap bit = bitmapfactory.decodebytearray(bytes, 0, bytes.length, options); 
    log.i("info", "图片大小：" + bit.getbytecount());//2665296  10661184 
    return bit; 
  } 
 
  /** 
   * 图片质量压缩 
   * 
   * @param bitmap 
   * @param quality 
   * @return 尺寸不变，质量变小 
   */ 
  public static bitmap compressbyquality(bitmap bitmap, int quality) { 
    bytearrayoutputstream baos = new bytearrayoutputstream(); 
    bitmap.compress(bitmap.compressformat.jpeg, quality, baos); 
    byte[] bytes = baos.tobytearray(); 
    bitmap bit = bitmapfactory.decodebytearray(bytes, 0, bytes.length); 
    log.i("info", "图片大小：" + bit.getbytecount());//10661184 
    return bit; 
  } 
 
  /** 
   * 图片质量压缩 
   * 
   * @param src 
   * @param maxbytesize 
   * @return 
   */ 
  public static bitmap compressbyquality(bitmap src, long maxbytesize) { 
    bytearrayoutputstream baos = new bytearrayoutputstream(); 
    int quality = 100; 
    src.compress(bitmap.compressformat.jpeg, quality, baos); 
    while (baos.tobytearray().length > maxbytesize && quality > 0) { 
      baos.reset(); 
      src.compress(bitmap.compressformat.jpeg, quality -= 5, baos); 
    } 
    if (quality < 0) return null; 
    byte[] bytes = baos.tobytearray(); 
    bitmap bit = bitmapfactory.decodebytearray(bytes, 0, bytes.length); 
    return bit; 
  } 
 
  public static bitmap compressbyformat(bitmap bitmap, int format) { 
    bytearrayoutputstream baos = new bytearrayoutputstream(); 
    bitmap.compress(bitmap.compressformat.jpeg, 100, baos); 
    byte[] bytes = baos.tobytearray(); 
    bitmap bit = bitmapfactory.decodebytearray(bytes, 0, bytes.length); 
    log.i("info", "图片大小：" + bit.getbytecount());//10661184 
    return bit; 
  } 
 
  /** 
   * matrix缩放 
   * 
   * @param bitmap 
   * @param scalewidth 
   * @param scaleheight 
   * @return 尺寸和大小变化 
   */ 
  public static bitmap getbitmapbysize(bitmap bitmap, float scalewidth, float scaleheight) { 
    matrix matrix = new matrix(); 
    matrix.postscale(scalewidth, scaleheight); 
    bitmap bit = bitmap.createbitmap(bitmap, 0, 0, bitmap.getwidth(), bitmap.getheight(), matrix, false); 
    log.i("info", "图片大小：" + bit.getbytecount()); 
    return bit; 
  } 
 
  /** 
   * 按照图片格式配置压缩 
   * 
   * @param path 
   * @param config alpha_8,argb_4444,argb_8888,rgb_565; 
   * @return rgb_565比argb_8888节省一半内存 
   */ 
  public static bitmap getbitmapbyformatconfig(string path, bitmap.config config) { 
    bitmapfactory.options options = new bitmapfactory.options(); 
    options.inpreferredconfig = config; 
    bitmap bitmap = bitmapfactory.decodefile(path, options); 
    log.i("info", "图片大小：" + bitmap.getbytecount()); 
    return bitmap; 
  } 
 
  /** 
   * 指定大小缩放 
   * 
   * @param bitmap 
   * @param width 
   * @param height 
   * @return 
   */ 
  public static bitmap getbitmapbyscalesize(bitmap bitmap, int width, int height) { 
    bitmap bit = bitmap.createscaledbitmap(bitmap, width, height, true); 
    log.i("info", "图片大小：" + bit.getbytecount()); 
    return bit; 
  } 
 
  /** 
   * 通过保存格式压缩 
   * 
   * @param bitmap 
   * @param format jpeg,png,webp 
   * @return 
   */ 
  public static bitmap getbitmapbyformat(bitmap bitmap, bitmap.compressformat format) { 
    bytearrayoutputstream baos = new bytearrayoutputstream(); 
    bitmap.compress(format, 100, baos); 
    byte[] bytes = baos.tobytearray(); 
    bitmap bit = bitmapfactory.decodebytearray(bytes, 0, bytes.length); 
    log.i("info", "图片大小：" + bit.getbytecount()); 
    return bit; 
  } 
 
  /** 
   * 文件加载压缩 
   * 
   * @param filepath 
   * @param insamplesize 
   * @return 
   */ 
  public static bitmap getbitmap(string filepath, int insamplesize) { 
    bitmapfactory.options options = new bitmapfactory.options(); 
    options.injustdecodebounds = true; 
    bitmapfactory.decodefile(filepath, options);//此时不耗费和占用内存 
    options.insamplesize = insamplesize; 
    options.injustdecodebounds = false; 
    return bitmapfactory.decodefile(filepath, options); 
  } 
 
  public static bitmap getbitmap(string filepath) { 
    return bitmapfactory.decodefile(filepath); 
  } 
 
  public static bitmap view2bitmap(view view) { 
    if (view == null) return null; 
    bitmap ret = bitmap.createbitmap(view.getwidth(), view.getheight(), bitmap.config.argb_8888); 
    canvas canvas = new canvas(ret); 
    drawable bgdrawable = view.getbackground(); 
    if (bgdrawable != null) { 
      bgdrawable.draw(canvas); 
    } else { 
      canvas.drawcolor(color.white); 
    } 
    view.draw(canvas); 
    return ret; 
  } 
 
  public static void savebitmap(bitmap bitmap) { 
    file file = new file(environment.getexternalstoragedirectory() + "/img.jpg"); 
    try { 
      fileoutputstream fileoutputstream = new fileoutputstream(file); 
      bitmap.compress(bitmap.compressformat.jpeg, 100, fileoutputstream); 
      fileoutputstream.flush(); 
      fileoutputstream.close(); 
    } catch (filenotfoundexception e) { 
      e.printstacktrace(); 
    } catch (ioexception e) { 
      e.printstacktrace(); 
    } 
  } 
 
  public static void savebitmap(bitmap bitmap,bitmap.compressformat format) { 
    file file = new file(environment.getexternalstoragedirectory() + "/img.jpg"); 
    try { 
      fileoutputstream fileoutputstream = new fileoutputstream(file); 
      bitmap.compress(format, 100, fileoutputstream); 
      fileoutputstream.flush(); 
      fileoutputstream.close(); 
    } catch (filenotfoundexception e) { 
      e.printstacktrace(); 
    } catch (ioexception e) { 
      e.printstacktrace(); 
    } 
  } 
} 

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