9

你们有没有一个想法，如何在任何四边形中扭曲图像？我想实现一个图像，你可以在任何方向拉任何角落，扭曲图像。任何人都知道如何做到这一点？我现在在 android 中使用和编写东西有一段时间了，但似乎 android 没有这样的功能。我真的不想写一个新的数学库:)。

问候，可以

4

5 回答 5

9

看起来你需要Canvas.drawBitmapMesh。Android SDK 中有一个示例展示了如何使用它。

您需要Matrix用于在Canvas. 您可以使用Matrix.polyToPoly方法轻松创建这样的转换，它将您的位图图像适合任何四边形。它看起来像这样：

matrix.setPolyToPoly(
        new float[] { 
            0, 0, 
            bitmap.getWidth(), 0
            0, bitmap.getHeight(),
            bitmap.getWidth(), bitmap.getHeight() 
        }, 0, 
        new float[] { 
            x0, y0, 
            x1, y1, 
            x2, y2,
            x3, y3
        }, 0, 
        4);

canvas.drawBitmap(bitmap, matrix, paint);

其中 x0-x3, y0-y3 是您的四边形顶点坐标。

于 2012-12-18T15:17:20.427 回答
4

@donmj 。我修复了你的代码。

public class PerspectiveDistortView extends View implements View.OnTouchListener {

private Paint paintRect, paintCircle;
public int LEFT;
public int TOP;
public int RIGHT;
public int BOTTOM;
Point CIRCLE_TOP_LEFT;
Point CIRCLE_TOP_RIGHT;
Point CIRCLE_BOTTOM_LEFT;
Point CIRCLE_BOTTOM_RIGHT;
private int lastX, lastY;
Bitmap image;
Matrix matrix2;
boolean isTouchCirclePoints = true;

public PerspectiveDistortView(Context context) {
    super(context);
    // TODO Auto-generated constructor stub
    init();
}

public PerspectiveDistortView(Context context, AttributeSet attrs) {
    super(context, attrs);
    // TODO Auto-generated constructor stub
    init();
}

public PerspectiveDistortView(Context context, AttributeSet attrs,
                              int defStyle) {
    super(context, attrs, defStyle);
    // TODO Auto-generated constructor stub
    init();
}

private void init() {
    this.setOnTouchListener(this);
    paintRect = new Paint();
    paintRect.setColor(0xffff0000);
    paintRect.setAntiAlias(true);
    paintRect.setDither(true);
    paintRect.setStyle(Paint.Style.STROKE);
    paintRect.setStrokeJoin(Paint.Join.BEVEL);
    paintRect.setStrokeCap(Paint.Cap.BUTT);
    paintRect.setStrokeWidth(3);
    paintCircle = new Paint();
    paintCircle.setColor(0xff000000);
    paintCircle.setAntiAlias(true);
    paintCircle.setDither(true);
    paintCircle.setStyle(Paint.Style.FILL_AND_STROKE);
    paintCircle.setStrokeJoin(Paint.Join.BEVEL);
    paintCircle.setStrokeCap(Paint.Cap.BUTT);

    LEFT = 90;
    TOP = 40;
    RIGHT = 500;
    BOTTOM = 700;
    CIRCLE_TOP_LEFT = new Point(LEFT, TOP);
    CIRCLE_TOP_RIGHT = new Point(RIGHT, TOP);
    CIRCLE_BOTTOM_LEFT = new Point(LEFT, BOTTOM);
    CIRCLE_BOTTOM_RIGHT = new Point(RIGHT, BOTTOM);

    image = BitmapFactory.decodeResource(getResources(), R.drawable.penguins);

    matrix2 = new Matrix();
}

@Override
protected void onDraw(Canvas canvas) {
    // Free Transform bitmap
    int bw = image.getWidth();
    int bh = image.getHeight();

    float[] pts = {
            // source
            0, 0,
            0, bh,
            bw, bh,
            bw, 0,
            // destination
            0, 0,
            0, 0,
            0, 0,
            0, 0};
    pts[8] = CIRCLE_TOP_LEFT.x;
    pts[9] = CIRCLE_TOP_LEFT.y;
    pts[10] = CIRCLE_BOTTOM_LEFT.x;
    pts[11] = CIRCLE_BOTTOM_LEFT.y;
    pts[12] = CIRCLE_BOTTOM_RIGHT.x;
    pts[13] = CIRCLE_BOTTOM_RIGHT.y;
    pts[14] = CIRCLE_TOP_RIGHT.x;
    pts[15] = CIRCLE_TOP_RIGHT.y;

    matrix2.setPolyToPoly(pts, 0, pts, 8, 4);
    canvas.drawBitmap(image, matrix2, null);
    isTouchCirclePoints = false;

    // line left
    canvas.drawLine(CIRCLE_TOP_LEFT.x, CIRCLE_TOP_LEFT.y, CIRCLE_BOTTOM_LEFT.x, CIRCLE_BOTTOM_LEFT.y, paintRect);
    // line top
    canvas.drawLine(CIRCLE_TOP_LEFT.x, CIRCLE_TOP_LEFT.y, CIRCLE_TOP_RIGHT.x, CIRCLE_TOP_RIGHT.y, paintRect);
    // line right
    canvas.drawLine(CIRCLE_TOP_RIGHT.x, CIRCLE_TOP_RIGHT.y, CIRCLE_BOTTOM_RIGHT.x, CIRCLE_BOTTOM_RIGHT.y, paintRect);
    // line bottom
    canvas.drawLine(CIRCLE_BOTTOM_LEFT.x, CIRCLE_BOTTOM_LEFT.y, CIRCLE_BOTTOM_RIGHT.x, CIRCLE_BOTTOM_RIGHT.y, paintRect);
    // circle top left
    canvas.drawCircle(CIRCLE_TOP_LEFT.x, CIRCLE_TOP_LEFT.y, 10, paintCircle);
    // circle top right
    canvas.drawCircle(CIRCLE_TOP_RIGHT.x, CIRCLE_TOP_RIGHT.y, 10, paintCircle);
    // circle bottom left
    canvas.drawCircle(CIRCLE_BOTTOM_LEFT.x, CIRCLE_BOTTOM_LEFT.y, 10, paintCircle);
    // circle bottom right
    canvas.drawCircle(CIRCLE_BOTTOM_RIGHT.x, CIRCLE_BOTTOM_RIGHT.y, 10, paintCircle);
}

@Override
public boolean onTouch(View view, MotionEvent event) {
    lastX = (int) event.getX();
    lastY = (int) event.getY();

    if (inCircle(lastX, lastY, CIRCLE_TOP_LEFT.x, CIRCLE_TOP_LEFT.y, 40)) {
        isTouchCirclePoints = true;
        CIRCLE_TOP_LEFT.set(lastX, lastY);
    } else if (inCircle(lastX, lastY, CIRCLE_TOP_RIGHT.x, CIRCLE_TOP_RIGHT.y, 40)) {
        isTouchCirclePoints = true;
        CIRCLE_TOP_RIGHT.set(lastX, lastY);
    } else if (inCircle(lastX, lastY, CIRCLE_BOTTOM_LEFT.x, CIRCLE_BOTTOM_LEFT.y, 40)) {
        isTouchCirclePoints = true;
        CIRCLE_BOTTOM_LEFT.set(lastX, lastY);
    } else if (inCircle(lastX, lastY, CIRCLE_BOTTOM_RIGHT.x, CIRCLE_BOTTOM_RIGHT.y, 40)) {
        isTouchCirclePoints = true;
        CIRCLE_BOTTOM_RIGHT.set(lastX, lastY);
    }
    invalidate();
    return true;
}

private boolean inCircle(float x, float y, float circleCenterX, float circleCenterY, float circleRadius) {
    double dx = Math.pow(x - circleCenterX, 2);
    double dy = Math.pow(y - circleCenterY, 2);

    if ((dx + dy) < Math.pow(circleRadius, 2)) {
        return true;
    } else {
        return false;
    }
}
}
于 2016-01-07T23:23:58.720 回答
3

你的代码有问题。尽管它是正确的方法，但您已经反转了 float[] 参数，如 Android 文档中所示：

public boolean setPolyToPoly (float[] src, int srcIndex, float[] dst, int dstIndex, int pointCount)
WHERE
src: The array of src [x,y] pairs (points)
...
dst: The array of dst [x,y] pairs (points)

因此，根据您的代码，矩阵应创建为：

matrix.setPolyToPoly(
        new float[] {
            x0, y0,
            x1, y1,
            x2, y2,
            x3, y3},
    0,
new float[] { 
        0, 0, 
        bitmap.getWidth(), 0
        0, bitmap.getHeight(),
        bitmap.getWidth(), bitmap.getHeight() 
    }, 0, 
    4);

通过这种方式，应用程序运行良好，如图所示：

在此处输入图像描述

另一方面，关于 user2498079 在评论中所说的低端设备计算问题，您可以在矩阵转换计算之前使用一些易于操作的技术来减小源图像大小（例如颜色深度） . 这将使低端手机更容易实现这一任务。

于 2015-09-30T16:26:56.663 回答
2

matrix.setPolyToPoly并且canvas.drawBitmap不能解决所有的矩阵变换。在这里，我找到了一个使用canvas.drawBitmapMesh.

在 Android 上的某些情况下，将图像扭曲为四边形会失败

于 2016-04-22T07:09:18.793 回答
1

我希望这有帮助。左上角、右上角除了左下角和右下角外都在工作。有人可以添加它。我不知道如何做底部部分。:)

public class PerspectiveDistortView extends View  implements OnTouchListener {

private Paint paintRect, paintCircle;
public int LEFT;
public int TOP;
public int RIGHT;
public int BOTTOM;
Point CIRCLE_TOP_LEFT;
Point CIRCLE_TOP_RIGHT;
Point CIRCLE_BOTTOM_LEFT;
Point CIRCLE_BOTTOM_RIGHT;
private int lastX, lastY;
Bitmap image;
Rect src, dst;
Matrix matrix2;
boolean isTouchCirclePoints = true;
float deform2 = 5f;

public PerspectiveDistortView(Context context) {
    super(context);
    // TODO Auto-generated constructor stub
    init();
}

public PerspectiveDistortView(Context context, AttributeSet attrs) {
    super(context, attrs);
    // TODO Auto-generated constructor stub
    init();
}

public PerspectiveDistortView(Context context, AttributeSet attrs,
        int defStyle) {
    super(context, attrs, defStyle);
    // TODO Auto-generated constructor stub
    init();
}

private void init(){
    this.setOnTouchListener(this);
    paintRect = new Paint();
    paintRect.setColor(0xffff0000);
    paintRect.setAntiAlias(true);
    paintRect.setDither(true);
    paintRect.setStyle(Paint.Style.STROKE);
    paintRect.setStrokeJoin(Paint.Join.BEVEL);
    paintRect.setStrokeCap(Paint.Cap.BUTT);
    paintRect.setStrokeWidth(3);
    paintCircle = new Paint();
    paintCircle.setColor(0xff000000);
    paintCircle.setAntiAlias(true);
    paintCircle.setDither(true);
    paintCircle.setStyle(Paint.Style.FILL_AND_STROKE);
    paintCircle.setStrokeJoin(Paint.Join.BEVEL);
    paintCircle.setStrokeCap(Paint.Cap.BUTT);

    LEFT = 90;
    TOP = 40;
    RIGHT = 500;
    BOTTOM = 700;
    CIRCLE_TOP_LEFT = new Point(LEFT, TOP);
    CIRCLE_TOP_RIGHT = new Point(RIGHT, TOP);
    CIRCLE_BOTTOM_LEFT = new Point(LEFT, BOTTOM);
    CIRCLE_BOTTOM_RIGHT = new Point(RIGHT, BOTTOM);

    image = BitmapFactory.decodeResource(getResources(), R.drawable.ai);

    src = new Rect();
    dst = new Rect();

    matrix2 = new Matrix();
}

@Override
protected void onDraw(Canvas canvas) {
    // draw image
    src.left = LEFT;
    src.top = TOP;
    src.right = RIGHT;
    src.bottom = BOTTOM + image.getHeight();

    dst.left = CIRCLE_TOP_LEFT.x;
    dst.top = CIRCLE_TOP_LEFT.y;
    dst.right = CIRCLE_TOP_RIGHT.x;
    dst.bottom = CIRCLE_BOTTOM_RIGHT.y;

    // Free Transform bitmap
        int bw = image.getWidth();
        int bh = image.getHeight();
        RectF src = new RectF(LEFT, TOP, bw, bh);
        RectF dst = new RectF(CIRCLE_TOP_LEFT.x + 35, CIRCLE_TOP_LEFT.y + 30, CIRCLE_TOP_RIGHT.x, CIRCLE_BOTTOM_RIGHT.y);
        matrix2.setRectToRect(src, dst, ScaleToFit.FILL);

        float[] pts = {
                       // source
                       0, 0, 
                       0, bh, 
                       bw, bh, 
                       bw, 0,
                       // destination
                       0, 0,
                       0, 0, 
                       0, 0, 
                       0, 0};
        matrix2.mapPoints(pts, 8, pts, 0, 4);
        int DX = 100;
        pts[10] -= CIRCLE_TOP_LEFT.x - LEFT; 
        pts[12] -= CIRCLE_TOP_RIGHT.x - RIGHT;
        pts[13] += 0;
        pts[14] += 0;
        pts[15] += CIRCLE_TOP_RIGHT.y - CIRCLE_TOP_LEFT.y;

        matrix2.setPolyToPoly(pts, 0, pts, 8, 4);
        canvas.drawBitmap(image, matrix2, null);
        isTouchCirclePoints = false;

    // line left
    canvas.drawLine(CIRCLE_TOP_LEFT.x, CIRCLE_TOP_LEFT.y, CIRCLE_BOTTOM_LEFT.x, CIRCLE_BOTTOM_LEFT.y, paintRect);
    // line top
    canvas.drawLine(CIRCLE_TOP_LEFT.x, CIRCLE_TOP_LEFT.y, CIRCLE_TOP_RIGHT.x, CIRCLE_TOP_RIGHT.y, paintRect);
    // line right
    canvas.drawLine(CIRCLE_TOP_RIGHT.x, CIRCLE_TOP_RIGHT.y, CIRCLE_BOTTOM_RIGHT.x, CIRCLE_BOTTOM_RIGHT.y, paintRect);
    // line bottom
    canvas.drawLine(CIRCLE_BOTTOM_LEFT.x, CIRCLE_BOTTOM_LEFT.y, CIRCLE_BOTTOM_RIGHT.x, CIRCLE_BOTTOM_RIGHT.y, paintRect);
    // circle top left
    canvas.drawCircle(CIRCLE_TOP_LEFT.x, CIRCLE_TOP_LEFT.y, 10, paintCircle);
    // circle top right
    canvas.drawCircle(CIRCLE_TOP_RIGHT.x, CIRCLE_TOP_RIGHT.y, 10, paintCircle);
    // circle bottom left
    canvas.drawCircle(CIRCLE_BOTTOM_LEFT.x, CIRCLE_BOTTOM_LEFT.y, 10, paintCircle);
    // circle bottom right
    canvas.drawCircle(CIRCLE_BOTTOM_RIGHT.x, CIRCLE_BOTTOM_RIGHT.y, 10, paintCircle);
}

@Override
public boolean onTouch(View view, MotionEvent event) {
    lastX = (int) event.getX();
    lastY = (int)event.getY();
    if (inCircle(lastX, lastY, CIRCLE_TOP_LEFT.x, CIRCLE_TOP_LEFT.y, 40))
    {
        isTouchCirclePoints = true;
        CIRCLE_TOP_LEFT.set(lastX, lastY);
    } else if (inCircle(lastX, lastY, CIRCLE_TOP_RIGHT.x, CIRCLE_TOP_RIGHT.y, 40))
    {
        isTouchCirclePoints = true;
        CIRCLE_TOP_RIGHT.set(lastX, lastY);
    } else if (inCircle(lastX, lastY, CIRCLE_BOTTOM_LEFT.x, CIRCLE_BOTTOM_LEFT.y, 40))
    {
        isTouchCirclePoints = true;
        CIRCLE_BOTTOM_LEFT.set(lastX, lastY);
    } else if (inCircle(lastX, lastY, CIRCLE_BOTTOM_RIGHT.x, CIRCLE_BOTTOM_RIGHT.y, 40))
    {
        isTouchCirclePoints = true;
        CIRCLE_BOTTOM_RIGHT.set(lastX, lastY);
    }
    invalidate();
    return true;
}

private boolean inCircle(float x, float y, float circleCenterX, float circleCenterY, float circleRadius) {
    double dx = Math.pow(x - circleCenterX, 2);
    double dy = Math.pow(y - circleCenterY, 2);

    if ((dx + dy) < Math.pow(circleRadius, 2)) {
        return true;
    } else {
        return false;
    }
}

}

于 2015-11-15T10:12:45.780 回答