如何将图像横盘或倒置？ [英] how to turn an image sideways or upside-down?

问题描述

我有一个自定义视图和我使用的onDraw（）来绘制到我的画布。我这个画布上绘制图像。

I have a custom view and i am using onDraw() to draw onto my canvas. I am drawing an image on this canvas.

我想打开图像上下颠倒有点像翻盖上的水平线作为参考。这是不一样的180度或-180度的旋转图像。

I want to turn the image upside down kinda like flip on a horizontal line as a reference. This is not the same as rotating the image by 180 deg or -180 deg.

同样，我希望镜像或以垂直线翻转sidways即因为它的支点或引用。再次，这是不一样的canvas.rotate（）提供

Likewise, i want to mirror or flip sidways i.e with a vertical line as it's pivot or reference. Again this is not the same as the canvas.rotate() provides.

我想知道如何做到这一点。我应该用一个矩阵还是帆布提供任何方法来那样做的旋转。

I am wondering how to do it. Should i use a matrix or does canvas provide any method to do it like that of a "rotate".

感谢。

推荐答案

您不能直接帆布做的。你需要绘制它之前实际修改的位图（使用矩阵）。幸运的是，这是一个非常简单的code要做到这一点：

You cannot do it with Canvas directly. You will need to actually modify the Bitmap (using Matrix) before drawing it. Luckily, it's a very simple code to do this:

public enum Direction { VERTICAL, HORIZONTAL };

/**
    Creates a new bitmap by flipping the specified bitmap
    vertically or horizontally.
    @param src        Bitmap to flip
    @param type       Flip direction (horizontal or vertical)
    @return           New bitmap created by flipping the given one
                      vertically or horizontally as specified by
                      the <code>type</code> parameter or
                      the original bitmap if an unknown type
                      is specified.
**/
public static Bitmap flip(Bitmap src, Direction type) {
    Matrix matrix = new Matrix();

    if(type == Direction.VERTICAL) {
        matrix.preScale(1.0f, -1.0f);
    }
    else if(type == Direction.HORIZONTAL) {
        matrix.preScale(-1.0f, 1.0f);
    } else {
        return src;
    }

    return Bitmap.createBitmap(src, 0, 0, src.getWidth(), src.getHeight(), matrix, true);
}

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