110

如何将图像放到画布上以便在该图像上绘图？

4

7 回答 7

198

在画布上绘制 Drawable 的好方法不是自己解码，而是让系统来做：

Drawable d = getResources().getDrawable(R.drawable.foobar, null);
d.setBounds(left, top, right, bottom);
d.draw(canvas);

这将适用于各种可绘制对象，而不仅仅是位图。这也意味着如果只有大小发生变化，您可以再次重复使用同一个可绘制对象。

于 2014-04-08T08:36:15.803 回答
39

您需要将图像加载为位图：

 Resources res = getResources();
 Bitmap bitmap = BitmapFactory.decodeResource(res, R.drawable.your_image);

然后使位图可变并在其上创建一个画布：

Canvas canvas = new Canvas(bitmap.copy(Bitmap.Config.ARGB_8888, true));

然后，您可以在画布上绘图。

于 2011-03-03T04:00:45.580 回答
15

你也可以使用这种方式。它会改变你的大drawble适合你的画布：

Resources res = getResources();
Bitmap bitmap = BitmapFactory.decodeResource(res, yourDrawable);
yourCanvas.drawBitmap(bitmap, 0, 0, yourPaint);
于 2015-03-29T18:13:36.213 回答
12 
Drawable d = ContextCompat.getDrawable(context, R.drawable.***)
d.setBounds(left, top, right, bottom);
d.draw(canvas);
于 2016-02-17T07:06:10.260 回答
8

尝试这个

Bitmap mBitmap = Bitmap.createScaledBitmap(Bitmap src, int dstWidth, int dstHeight, boolean filter);

protected void onDraw(Canvas canvas) {
            canvas.drawColor(0xFFAAAAAA);
            canvas.drawBitmap(mBitmap, 0, 0, mBitmapPaint);

        }
于 2011-03-03T04:00:26.367 回答
2 
package com.android.jigsawtest;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.view.SurfaceHolder;
import android.view.SurfaceView;

public class SurafaceClass extends SurfaceView implements
        SurfaceHolder.Callback {
    Bitmap mBitmap;
Paint paint =new Paint();
    public SurafaceClass(Context context) {
        super(context);
        mBitmap = BitmapFactory.decodeResource(getResources(), R.drawable.icon);
        // TODO Auto-generated constructor stub
    }

    @Override
    public void surfaceChanged(SurfaceHolder holder, int format, int width,
            int height) {
        // TODO Auto-generated method stub

    }

    @Override
    public void surfaceCreated(SurfaceHolder holder) {
        // TODO Auto-generated method stub

    }

    @Override
    public void surfaceDestroyed(SurfaceHolder holder) {
        // TODO Auto-generated method stub

    }

    @Override
    protected void onDraw(Canvas canvas) {
        canvas.drawColor(Color.BLACK);
        canvas.drawBitmap(mBitmap, 0, 0, paint);

    }

}
于 2012-01-21T07:31:33.870 回答
1

为了保持我的矢量可绘制对象的纵横比，我这样做了：

val drawable = resources.getDrawable(R.drawable.my_vector, null)
val aspectRatio = drawable.intrinsicWidth.toFloat() / drawable.intrinsicHeight
val desiredWidthInPx = 100
val derivedHeightInPx = (desiredWidthInPx / aspectRatio).toInt()
drawable.setBounds(0, 0, desiredWidthInPx, derivedHeightInPx)
drawable.draw(canvas)
于 2021-05-21T14:37:53.120 回答