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阅读五分钟，每日十点，和您一起终身学习，这里是程序员 Android

Drawable 使用方法详解请看上篇文章.
Drawable 使用方法详解

本篇文章主要介绍 Android 开发中的部分知识点，通过阅读本篇文章，您将收获以下内容:

1. 从资源中获取 Bitmap
2. Bitmap —-> byte[]
3. byte[] —-> Bitmap
4. Bitmap 缩放方法
5. Drawable —-> Bitmap
6. 圆角图片
7. 获取带倒影的图片
8. bitmap —-> Drawable
9. drawable 缩放，先转 bitmap 后缩放

1. 从资源中获取 Bitmap

    // 1. 从资源中获取 Bitmap
    public void UseBitmap(Context context, ImageView imageView, int drawableId) {Bitmap bitmap = BitmapFactory.decodeResource(context.getResources(),
                drawableId);
        imageView.setImageBitmap(bitmap);

    }

2. Bitmap —-> byte[]

    // 2.Bitmap ---> byte[]
    public byte[] BitmapToBytes(Bitmap bitmap) {ByteArrayOutputStream baos = new ByteArrayOutputStream();
        bitmap.compress(Bitmap.CompressFormat.PNG, 100, baos);
        return baos.toByteArray();}

3. byte[] —-> Bitmap

    // 3.byte[] ---->bitmap
    public Bitmap BytesToBitmap(byte[] b) {if (b.length != 0) {return BitmapFactory.decodeByteArray(b, 0, b.length);
        } else {return null;}
    }

4. Bitmap 缩放方法

    // 4.Bitmap 缩放方法
    public static Bitmap ZoomBitmap(Bitmap bitmap, int width, int heigh) {int w = bitmap.getWidth();
        int h = bitmap.getHeight();
        Matrix matrix = new Matrix();
        float scalewidth = (float) width / w;
        float scaleheigh = (float) heigh / h;
        matrix.postScale(scalewidth, scaleheigh);
        Bitmap newBmp = Bitmap.createBitmap(bitmap, 0, 0, w, h, matrix, true);
        return newBmp;

    }

5. Drawable —-> Bitmap

    // 5. Drawable----> Bitmap
    public static Bitmap DrawableToBitmap(Drawable drawable) {

        // 获取 drawable 长宽
        int width = drawable.getIntrinsicWidth();
        int heigh = drawable.getIntrinsicHeight();

        drawable.setBounds(0, 0, width, heigh);

        // 获取 drawable 的颜色格式
        Bitmap.Config config = drawable.getOpacity() != PixelFormat.OPAQUE ? Bitmap.Config.ARGB_8888
                : Bitmap.Config.RGB_565;
        // 创建 bitmap
        Bitmap bitmap = Bitmap.createBitmap(width, heigh, config);
        // 创建 bitmap 画布
        Canvas canvas = new Canvas(bitmap);
        // 将 drawable 内容画到画布中
        drawable.draw(canvas);
        return bitmap;
    }

6. 圆角图片

- 实现效果如下：

• 实现代码如下：

    // 6. 圆角图片
    public static Bitmap SetRoundCornerBitmap(Bitmap bitmap, float roundPx) {int width = bitmap.getWidth();
        int heigh = bitmap.getHeight();
        // 创建输出 bitmap 对象
        Bitmap outmap = Bitmap.createBitmap(width, heigh,
                Bitmap.Config.ARGB_8888);
        Canvas canvas = new Canvas(outmap);
        final int color = 0xff424242;
        final Paint paint = new Paint();
        final Rect rect = new Rect(0, 0, width, heigh);
        final RectF rectf = new RectF(rect);
        paint.setAntiAlias(true);
        canvas.drawARGB(0, 0, 0, 0);
        paint.setColor(color);
        canvas.drawRoundRect(rectf, roundPx, roundPx, paint);
        paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN));
        canvas.drawBitmap(bitmap, rect, rect, paint);

        return outmap;
    }

7. 获取带倒影的图片

• 实现效果如下：

• 实现代码如下：

    // 7. 获取带倒影的图片
    public static Bitmap CreateReflectionImageWithOrigin(Bitmap bitmap) {

        final int reflectionGap = 4;
        int w = bitmap.getWidth();
        int h = bitmap.getHeight();
        Matrix matrix = new Matrix();
        matrix.preScale(1, -1);

        Bitmap reflectionImage = Bitmap.createBitmap(bitmap, 0, h / 2, w,
                h / 2, matrix, false);

        Bitmap bitmapWithReflection = Bitmap.createBitmap(w, (h + h / 2),
                Bitmap.Config.ARGB_8888);
        Canvas canvas = new Canvas(bitmapWithReflection);
        canvas.drawBitmap(bitmap, 0, 0, null);
        Paint deafalutPaint = new Paint();
        canvas.drawRect(0, h, w, h + reflectionGap, deafalutPaint);

        canvas.drawBitmap(reflectionImage, 0, h + reflectionGap, null);

        Paint paint = new Paint();
        LinearGradient shader = new LinearGradient(0, bitmap.getHeight(), 0,
                bitmapWithReflection.getHeight() + reflectionGap, 0x70ffffff,
                0x00ffffff, Shader.TileMode.CLAMP);
        paint.setShader(shader);
        // Set the Transfer mode to be porter duff and destination in
        paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.DST_IN));
        // Draw a rectangle using the paint with our linear gradient
        canvas.drawRect(0, h, w, bitmapWithReflection.getHeight()
                + reflectionGap, paint);
        return bitmapWithReflection;
    }

8. bitmap —-> Drawable

    // 8. bitmap ---Drawable
    public static Drawable BitmapToDrawable(Bitmap bitmap, Context context) {BitmapDrawable drawbale = new BitmapDrawable(context.getResources(),
                bitmap);
        return drawbale;
    }

9. drawable 缩放，先转 bitmap 后缩放

drawable缩放，先转 bitmap，调用 5 中的方法 后缩放。

    // 9. drawable 进行缩放 ---> bitmap 然后比对 bitmap 进行缩放
    public static Drawable ZoomDrawable(Drawable drawable, int w, int h) {int width = drawable.getIntrinsicWidth();
        int height = drawable.getIntrinsicHeight();
        // 调用 5 中 drawable 转换成 bitmap
        Bitmap oldbmp = DrawableToBitmap(drawable);

        // 创建操作图片用的 Matrix 对象
        Matrix matrix = new Matrix();
        // 计算缩放比例
        float sx = ((float) w / width);
        float sy = ((float) h / height);
        // 设置缩放比例
        matrix.postScale(sx, sy);
        // 建立新的 bitmap，其内容是对原 bitmap 的缩放后的图
        Bitmap newbmp = Bitmap.createBitmap(oldbmp, 0, 0, width, height,
                matrix, true);
        return new BitmapDrawable(newbmp);
    }

至此，本篇已结束，如有不对的地方，欢迎您的建议与指正。同时期待您的关注，感谢您的阅读，谢谢！