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保存后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，非整數倍四舍五入，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(); } } } 感謝閱讀，希望能幫助到大家，謝謝大家對本站的支持！
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