二次采样质量压缩_色度二次采样压缩比怎么算-优快云博客

本文链接：https://blog.youkuaiyun.com/css0902/article/details/73825907

本文介绍了Android中两种图片压缩技术：二次采样和质量压缩。通过二次采样调整图片大小，以适应指定尺寸，减少内存消耗；质量压缩则通过调整JPEG压缩比例来降低文件大小。示例代码展示了如何实现这两种压缩方法。

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xml布局：
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context="com.andy.image.MainActivity">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1"
        android:orientation="vertical">
        <TextView
            android:id="@+id/tv1"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:textSize="18sp"
            android:text="原图"/>
        <ImageView
            android:id="@+id/image1"
            android:layout_width="match_parent"
            android:layout_height="match_parent"/>

    </LinearLayout>
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1"
        android:orientation="vertical">
        <TextView
            android:id="@+id/tv2"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:textSize="18sp"
            android:text="二次采样"/>
        <ImageView
            android:id="@+id/image2"
            android:layout_width="match_parent"
            android:layout_height="match_parent"/>
    </LinearLayout>
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1"
        android:orientation="vertical">
        <TextView
            android:id="@+id/tv3"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:textSize="18sp"
            android:text="质量压缩"/>
        <ImageView
            android:id="@+id/image3"
            android:layout_width="match_parent"
            android:layout_height="match_parent"/>
    </LinearLayout>
</LinearLayout>



二次采样：
 private void doubleSampling() {
    try {
        InputStream in = getAssets().open("mm.jpg");

        BitmapFactory.Options options = new BitmapFactory.Options();
        options.inJustDecodeBounds = true;
        BitmapFactory.decodeStream(in, null, options);
        int inSampleSize = 1;

        int width = options.outWidth;
        int height = options.outHeight;

        //400*300
        while (width / inSampleSize > 400 || height / inSampleSize > 300) {
            inSampleSize *= 2;
        }

        options.inSampleSize = inSampleSize;
        options.inJustDecodeBounds = false;
        Bitmap bitmap = BitmapFactory.decodeStream(in, null, options);

       // image2.setImageBitmap(bitmap);
        //showBitmap(bitmap, tv2);

    } catch (IOException e) {
        e.printStackTrace();
    }
}

质量压缩：
private void compressImage() {
    try {
        InputStream in = getAssets().open("mm.jpg");
        Bitmap bitmap = BitmapFactory.decodeStream(in);

        ByteArrayOutputStream stream = new ByteArrayOutputStream();
        bitmap.compress(Bitmap.CompressFormat.JPEG, 10, stream);

        bitmap.recycle();
        byte[] bytes=stream.toByteArray();
        Bitmap bitmap1 = BitmapFactory.decodeByteArray(bytes, 0, bytes.length);

        //image3.setImageBitmap(bitmap1);
        //showBitmap(bitmap1,tv3);


    } catch (IOException e) {
        e.printStackTrace();
    }


}
显示图片的高宽：
private void showBitmap(Bitmap bitmap, TextView tv) {
    int width = bitmap.getWidth();
    int height = bitmap.getHeight();
    int size = bitmap.getRowBytes() * bitmap.getHeight();
    String fileSize = Formatter.formatFileSize(this, size);

    //tv.setText(tv.getText() + "----" + width + "*" + height + "------" + size + "---" + fileSize);

}