Android教程-图像操作-Bitmap

/**
 * 裁剪
 *
 * @param bitmap 原图
 * @param l      原图 - 左
 * @param t      原图 - 上
 * @param r      原图 - 右
 * @param b      原图 - 下
 * @return 裁剪后图片
 */
private Bitmap cropBitmap(Bitmap bitmap, int l, int t, int r, int b) {
    int width = bitmap.getWidth();
    int height = bitmap.getHeight();
    int maxWidth = width - l;
    int maxHeight = height - t;

    if (r > maxWidth) {
        r = maxWidth;
    }
    if (b > maxHeight) {
        b = maxHeight;
    }
    Bitmap newIMG = Bitmap.createBitmap(bitmap, l, t, r - l, b - t, null, false);
    if (newIMG.equals(bitmap)) {
        return newIMG;
    }
    bitmap.recycle();
    return newIMG;
}

/**
 * 指定位置绘制边框
 *
 * @param bitmap
 * @param l
 * @param t
 * @param r
 * @param b
 * @param lineWidth
 * @return
 */
private static Bitmap drawFrame(Bitmap bitmap, int l, int t, int r, int b, int lineWidth, @ColorInt int lineColor) {
    if (bitmap == null) {
        return null;
    }
    Bitmap copy = bitmap.copy(Bitmap.Config.ARGB_8888, true);
    bitmap.recycle();
    //创建画布
    Canvas canvas = new Canvas(copy);
    //画笔
    Paint paint = new Paint();
    //设置线宽。单位为像素
    paint.setStrokeWidth(lineWidth);
    //抗锯齿
    paint.setAntiAlias(true);
    //画笔颜色
    paint.setColor(lineColor);
    //画笔风格，描边
    paint.setStyle(Paint.Style.STROKE);
    canvas.drawRect(l, t, r, b, paint);
    canvas.save();
    return copy;
}

/**
 * 根据给定的宽和高进行拉伸
 *
 * @param origin    原图
 * @param newWidth  新图的宽
 * @param newHeight 新图的高
 * @return new Bitmap
 */
private Bitmap scaleBitmap(Bitmap origin, int newWidth, int newHeight) {
    if (origin == null) {
        return null;
    }
    int height = origin.getHeight();
    int width = origin.getWidth();
    float scaleWidth = ((float) newWidth) / width;
    float scaleHeight = ((float) newHeight) / height;
    Matrix matrix = new Matrix();
    matrix.postScale(scaleWidth, scaleHeight);// 使用后乘
    Bitmap newBM = Bitmap.createBitmap(origin, 0, 0, width, height, matrix, false);
    if (!origin.isRecycled()) {
        origin.recycle();
    }
    return newBM;
}

/**
 * 按比例缩放图片
 *
 * @param origin 原图
 * @param ratio  比例
 * @return 新的bitmap
 */
private Bitmap scaleBitmap(Bitmap origin, float ratio) {
    if (origin == null) {
        return null;
    }
    int width = origin.getWidth();
    int height = origin.getHeight();
    Matrix matrix = new Matrix();
    matrix.preScale(ratio, ratio);
    Bitmap newBM = Bitmap.createBitmap(origin, 0, 0, width, height, matrix, false);
    if (newBM.equals(origin)) {
        return newBM;
    }
    origin.recycle();
    return newBM;
}

/**
 * 选择变换
 *
 * @param origin 原图
 * @param alpha  旋转角度，可正可负
 * @return 旋转后的图片
 */
private Bitmap rotateBitmap(Bitmap origin, float alpha) {
    if (origin == null) {
        return null;
    }
    int width = origin.getWidth();
    int height = origin.getHeight();
    Matrix matrix = new Matrix();
    matrix.setRotate(alpha);
    // 围绕原地进行旋转
    Bitmap newBM = Bitmap.createBitmap(origin, 0, 0, width, height, matrix, false);
    if (newBM.equals(origin)) {
        return newBM;
    }
    origin.recycle();
    return newBM;
}

/**
 * 偏移效果
 *
 * @param origin 原图
 * @return 偏移后的bitmap
 */
private Bitmap skewBitmap(Bitmap origin) {
    if (origin == null) {
        return null;
    }
    int width = origin.getWidth();
    int height = origin.getHeight();
    Matrix matrix = new Matrix();
    matrix.postSkew(-0.6f, -0.3f);
    Bitmap newBM = Bitmap.createBitmap(origin, 0, 0, width, height, matrix, false);
    if (newBM.equals(origin)) {
        return newBM;
    }
    origin.recycle();
    return newBM;
}