安卓：旋转图像围绕中心 [英] Android: Rotation of image around the center

问题描述

我想绕中心的图像。这个工程一般采用RotateAnimation，但我想把它快一点。我现在使用SurfaceView模式有独立的绘画主题。

I'm trying to rotate an image around the center. This works generally using RotateAnimation, but I want to have it a bit faster. I'm now using the SurfaceView pattern with a separate drawing thread.

这是code，它正确绘制位图（取决于外部标题）

This is code, which draws the bitmap correctly (depending on the outer "heading")

标题=度角， 位图=位图， 瓦特=宽度的位图， 位图的H =身高

heading = angle in degrees, bitmap = the bitmap, w = width of the bitmap, h = height of the bitmap.

    Matrix m = new Matrix();
    m.preRotate(heading, w/2, h/2);
    m.setTranslate(50,50);

    canvas.drawBitmap(bitmap, m, null);

缺点：该图像是一个圆，在code以上会产生明显的锯齿现象......

Drawback: The image is a circle and the code above produces visible aliasing effects...

在code以下也旋转图像，但同时转动（从0到45度顺时针说）的新形象举措底部/右侧的中心。我想，偏心的效果是由于新的图像的放大宽/高？然而，这code不会产生混淆，如果过滤器= true的设置。有没有办法使用code＃1，但有某种抗锯齿或使用code＃2，但摆脱中心运动？

The code below is also rotating the image, but while rotating (say from 0 to 45 degrees clockwise) the center of the new image moves bottom/right. I suppose, the eccentric effect is due to the enlarged width/height of the new image ?? However, this code doesn't produce aliasing, if filter=true is set. Is there a way to use code #1 but have sort of anti-aliasing or use code #2 but getting rid of the center movement?

    Matrix m = new Matrix();
    m.preRotate(heading, w/2, h/2);
    m.setTranslate(50,50);

    Bitmap rbmp = Bitmap.createBitmap(bitmap, 0, 0, w, h, m, true);
    canvas.drawBitmap(rbmp, 50, 50, null);

更新：由于正确版本的code＃在此线程的讨论2（抗锯齿的和的正确旋转）的结果是这样（的50,50省略偏移）

UPDATE: As result of the discussion in this thread the correct version of code #2 (anti-aliasing and correct rotation) would look like this (offset of 50,50 omitted):

        Matrix m = new Matrix();

        m.setRotate(heading, w/2, h/2);
        Bitmap rbpm = Bitmap.createBitmap(bitmap, 0, 0, w, h, m, true);
        canvas.drawBitmap(rbpm, (w - rbpm.getWidth())/2, (h - rbpm.getHeight())/2, null);

感谢。

推荐答案

查找原始图像的中心和新的形象和中心的使用：

Find the center of the original image and for the new image and center using that:

Matrix minMatrix = new Matrix();
//height and width are set earlier.
Bitmap minBitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
Canvas minCanvas = new Canvas(minBitmap);

int minwidth = bitmapMin.getWidth();  
int minheight = bitmapMin.getHeight();
int centrex = minwidth/2;
int centrey = minheight/2;

minMatrix.setRotate(mindegrees, centrex, centrey);
Bitmap newmin = Bitmap.createBitmap(minBitmap, 0, 0, (int) minwidth, (int) minheight, minMatrix, true);

minCanvas.drawBitmap(newmin, (centrex - newmin.getWidth()/2), (centrey - newmin.getHeight()/2), null);
minCanvas.setBitmap(minBitmap);

这篇关于安卓：旋转图像围绕中心的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！