android图片的缩放、圆角处理

android中图片缩放方法有三种：1，bitmapFactory；2，bitmap+metrix；3，thumbUtil

方法一：bitmapFactory：

public static Bitmap resizeBitmapByFactory(String path, int w, int h) {
        BitmapFactory.Options option = new BitmapFactory.Options();
        option.inJustDecodeBounds = true;
        Bitmap bitmap = BitmapFactory.decodeFile(path, option);
        int outWidth = option.outWidth;
        int outHeight = option.outHeight;
        option.inDither = false;
        option.inPreferredConfig = Bitmap.Config.ARGB_8888;

        if (outWidth != 0 && outHeight != 0 && w != 0 && h != 0) {
            int sampleSize = (outWidth / w + outHeight / h) / 2;
            option.inSampleSize = sampleSize;
        }

        option.inJustDecodeBounds = false;
        return BitmapFactory.decodeFile(path, option);

    }

方法二：bitmap+metrix

public static Bitmap resizeBitmapByMetrix(Bitmap bitmap, int w, int h) {
        Bitmap BitmapOrg = bitmap;
        int width = BitmapOrg.getWidth();
        int height = BitmapOrg.getHeight();
        int newWidth = w;
        int newHeight = h;

        float scaleWidth = ((float) newWidth) / width;
        float scaleHeight = ((float) newHeight) / height;

        Matrix matrix = new Matrix();
        matrix.postScale(scaleWidth, scaleHeight);
        // if you want to rotate the Bitmap
        // matrix.postRotate(45);
        Bitmap resizedBitmap = Bitmap.createBitmap(BitmapOrg, 0, 0, width,
                height, matrix, true);
        return resizedBitmap;
    }

方法三，使用系统自带的thumbutil：

public static Bitmap resizeBitmapByUtil(Bitmap bitmap, int w, int h) {
        return ThumbnailUtils.extractThumbnail(bitmap, w, h);
    }

三个方法消耗的时间为：72，9，13不过怀疑方法一消耗的时间有可能是由于从文件中加载图片所致。这点待定

二、实现图片的圆角效果

public static Bitmap toRoundCornerBitmap(Bitmap bitmap, int cornerPixel) {
        Bitmap output = Bitmap.createBitmap(bitmap.getWidth(),
                bitmap.getHeight(), Config.ARGB_8888);

        Canvas canvas = new Canvas(output);

        final int color = 0xff424242;

        final Paint paint = new Paint();

        final Rect rect = new Rect(0, 0, bitmap.getWidth(), bitmap.getHeight());

        final RectF rectF = new RectF(rect);

        final float roundPx = cornerPixel;

        paint.setAntiAlias(true);

        canvas.drawARGB(0, 0, 0, 0);

        paint.setColor(color);

        canvas.drawRoundRect(rectF, roundPx, roundPx, paint);

        paint.setXfermode(new PorterDuffXfermode(Mode.SRC_IN));

        canvas.drawBitmap(bitmap, rect, rect, paint);
        return output;
    }

三、实现图片缩放，背景为圆角图片，则这个背景可以用图形资源文件来实现。

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle">
    <gradient
        android:angle="90"
        android:endColor="#00000000"
        android:startColor="#00000000" />  

    <corners
        android:bottomLeftRadius="12dp"
        android:bottomRightRadius="12dp"
        android:topLeftRadius="12dp"
        android:topRightRadius="12dp" />  

    <stroke
        android:width="1dip"
        android:color="#eee" />
    <solid
        android:color="#000"/>
    <padding
        android:top="5dp"
        android:bottom="5dp"/>

</shape>