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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