Android圖片壓縮幾種方式總結

Android圖片壓縮幾種方式總結

圖片壓縮在Android開發中很常見也很重要，防止圖片的OOM也是壓縮的重要原因。

首先看下Bitmap圖片文件的大小的決定因素：

Bitmap所占用的內存 = 圖片長度 x 圖片寬度 x 一個像素點占用的字節數。3個參數，任意減少一個的值，就達到了壓縮的效果。

接下來看下Bitmap圖片的幾種格式的特點：

ALPHA_8
 表示8位Alpha位圖,即A=8,一個像素點占用1個字節,它沒有顏色,只有透明度
 ARGB_4444
表示16位ARGB位圖，即A=4,R=4,G=4,B=4,一個像素點占4+4+4+4=16位，2個字節
ARGB_8888
表示32位ARGB位圖，即A=8,R=8,G=8,B=8,一個像素點占8+8+8+8=32位，4個字節
RGB_565
表示16位RGB位圖,即R=5,G=6,B=5,它沒有透明度,一個像素點占5+6+5=16位，2個字節

如果進行圖片格式的壓縮的話，一般情況下都是ARGB_8888轉為RGB565進行壓縮。

寫了一個工具類，基本上列舉了android上圖片的幾種基本壓縮方式：

1.質量壓縮

2.采樣率壓縮

3.尺寸壓縮

4.Matrix壓縮

5.圖片格式的壓縮，例如PNG和JPG保存後的圖片大小是不同的

public class Utils { 
 
  /** 
   * 采樣率壓縮 
   * 
   * @param bitmap 
   * @param sampleSize 采樣率為2的整數倍，非整數倍四捨五入，如4的話，就是原圖的1/4 
   * @return 尺寸變化 
   */ 
  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", "圖片大小：" + bit.getByteCount());//2665296  10661184 
    return bit; 
  } 
 
  /** 
   * 圖片質量壓縮 
   * 
   * @param bitmap 
   * @param quality 
   * @return 尺寸不變，質量變小 
   */ 
  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", "圖片大小：" + bit.getByteCount());//10661184 
    return bit; 
  } 
 
  /** 
   * 圖片質量壓縮 
   * 
   * @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", "圖片大小：" + bit.getByteCount());//10661184 
    return bit; 
  } 
 
  /** 
   * Matrix縮放 
   * 
   * @param bitmap 
   * @param scaleWidth 
   * @param scaleHeight 
   * @return 尺寸和大小變化 
   */ 
  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", "圖片大小：" + bit.getByteCount()); 
    return bit; 
  } 
 
  /** 
   * 按照圖片格式配置壓縮 
   * 
   * @param path 
   * @param config ALPHA_8,ARGB_4444,ARGB_8888,RGB_565; 
   * @return RGB_565比ARGB_8888節省一半內存 
   */ 
  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", "圖片大小：" + bitmap.getByteCount()); 
    return bitmap; 
  } 
 
  /** 
   * 指定大小縮放 
   * 
   * @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", "圖片大小：" + bit.getByteCount()); 
    return bit; 
  } 
 
  /** 
   * 通過保存格式壓縮 
   * 
   * @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", "圖片大小：" + bit.getByteCount()); 
    return bit; 
  } 
 
  /** 
   * 文件加載壓縮 
   * 
   * @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);//此時不耗費和占用內存 
    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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