我需要捏缩放和拖动/平移图像，所以我实现了scaleimageview。 但是我放大的越多，图像越模糊。 我现在差不多3天寻找解决方案了。 我的代码看起来像这样（我使用Xamarin for Android）：
using Android.Views;
using Android.Widget;
namespace test
{
public class ScaleImageViewGestureDetector : GestureDetector.SimpleOnGestureListener
{
private readonly ScaleImageView m_ScaleImageView;
public ScaleImageViewGestureDetector(ScaleImageView imageView)
{
m_ScaleImageView = imageView;
}
public override bool OnDown(MotionEvent e)
{
return true;
}
public override bool OnDoubleTap(MotionEvent e)
{
m_ScaleImageView.MaxZoomTo((int)e.GetX(), (int)e.GetY());
m_ScaleImageView.Cutting();
return true;
}
}
public class ScaleImageView : ImageView, View.IOnTouchListener
{
private Context m_Context;
private float m_MaxScale = 2.0f;
private Matrix m_Matrix;
private float[] m_MatrixValues = new float[9];
private int m_Width;
private int m_Height;
private int m_IntrinsicWidth;
private int m_IntrinsicHeight;
private float m_Scale;
private float m_MinScale;
private float m_PreviousDistance;
private int m_PreviousMoveX;
private int m_PreviousMoveY;
private bool m_IsScaling;
private GestureDetector m_GestureDetector;
public ScaleImageView(Context context, IAttributeSet attrs) :
base(context, attrs)
{
m_Context = context;
Initialize();
}
public ScaleImageView(Context context, IAttributeSet attrs, int defStyle) :
base(context, attrs, defStyle)
{
m_Context = context;
Initialize();
}
public override void SetImageBitmap(Bitmap bm)
{
base.SetImageBitmap(bm);
this.Initialize();
}
public override void SetImageResource(int resId)
{
base.SetImageResource(resId);
this.Initialize();
}
private void Initialize()
{
this.SetScaleType(ScaleType.Matrix);
m_Matrix = new Matrix();
if (Drawable != null)
{
m_IntrinsicWidth = Drawable.IntrinsicWidth;
m_IntrinsicHeight = Drawable.IntrinsicHeight;
this.SetOnTouchListener(this);
}
m_GestureDetector = new GestureDetector(m_Context, new ScaleImageViewGestureDetector(this));
}
protected override bool SetFrame(int l, int t, int r, int b)//left top right bottom
{
m_Width = r - l;
m_Height = b - t;
Console.WriteLine ("test");
Console.WriteLine (m_Width.ToString ());
Console.WriteLine (m_Height.ToString ());
m_Matrix.Reset();
var r_norm = r - l;
m_Scale = (float)r_norm / (float)m_IntrinsicWidth;
ImageMatrix = m_Matrix;
double height = Resources.DisplayMetrics.HeightPixels;
double width = Resources.DisplayMetrics.WidthPixels;
float scaleFactor = (float)(height/m_IntrinsicHeight);
//don't take screen height, there's a tabbar on the bottom of the screen!
m_Matrix.PostTranslate( (float) ((width-m_IntrinsicWidth)/2.00f),(float) ((m_Height-m_IntrinsicHeight)/2.00f));
m_MinScale = scaleFactor;
ZoomTo(m_Scale, m_Width / 2, m_Height / 2);
Cutting();
return base.SetFrame(l, t, r, b);
}
private float GetValue(Matrix matrix, int whichValue)
{
matrix.GetValues(m_MatrixValues);
return m_MatrixValues[whichValue];
}
public float Scale
{
get { return this.GetValue(m_Matrix, Matrix.MscaleX); }
}
public float TranslateX
{
get { return this.GetValue(m_Matrix, Matrix.MtransX); }
}
public float TranslateY
{
get { return this.GetValue(m_Matrix, Matrix.MtransY); }
}
public void MaxZoomTo(int x, int y)
{
if (this.m_MinScale != this.Scale && (Scale - m_MinScale) > 0.1f)
{
var scale = m_MinScale / Scale;
ZoomTo(scale, x, y);
}
else
{
var scale = m_MaxScale / Scale;
ZoomTo(scale, x, y);
}
}
public void ZoomTo(float scale, int x, int y)
{
if (Scale * scale < m_MinScale)
{
scale = m_MinScale / Scale;
}
else
{
if (scale >= 1 && Scale * scale > m_MaxScale)
{
scale = m_MaxScale / Scale;
}
}
m_Matrix.PostScale(scale, scale);
//move to center
m_Matrix.PostTranslate(-(m_Width * scale - m_Width) / 2, -(m_Height * scale - m_Height) / 2);
//move x and y distance
m_Matrix.PostTranslate(-(x - (m_Width / 2)) * scale, 0);
m_Matrix.PostTranslate(0, -(y - (m_Height / 2)) * scale);
ImageMatrix = m_Matrix;
}
public void Cutting()
{
var width = (int)(m_IntrinsicWidth * Scale);
var height = (int)(m_IntrinsicHeight * Scale);
if (TranslateX < -(width - m_Width))
{
m_Matrix.PostTranslate(-(TranslateX + width - m_Width), 0);
}
if (TranslateX > 0)
{
m_Matrix.PostTranslate(-TranslateX, 0);
}
if (TranslateY < -(height - m_Height))
{
m_Matrix.PostTranslate(0, -(TranslateY + height - m_Height));
}
if (TranslateY > 0)
{
m_Matrix.PostTranslate(0, -TranslateY);
}
if (width < m_Width)
{
m_Matrix.PostTranslate((m_Width - width) / 2, 0);
}
if (height < m_Height)
{
m_Matrix.PostTranslate(0, (m_Height - height) / 2);
}
ImageMatrix = m_Matrix;
}
private float Distance(float x0, float x1, float y0, float y1)
{
var x = x0 - x1;
var y = y0 - y1;
return FloatMath.Sqrt(x * x + y * y);
}
private float DispDistance()
{
return FloatMath.Sqrt(m_Width * m_Width + m_Height * m_Height);
}
public override bool OnTouchEvent(MotionEvent e)
{
if (m_GestureDetector.OnTouchEvent(e))
{
m_PreviousMoveX = (int)e.GetX();
m_PreviousMoveY = (int)e.GetY();
return true;
}
var touchCount = e.PointerCount;
switch (e.Action)
{
case MotionEventActions.Down:
case MotionEventActions.Pointer1Down:
case MotionEventActions.Pointer2Down:
{
if (touchCount >= 2)
{
var distance = this.Distance(e.GetX(0), e.GetX(1), e.GetY(0), e.GetY(1));
m_PreviousDistance = distance;
m_IsScaling = true;
}
}
break;
case MotionEventActions.Move:
{
if (touchCount >= 2 && m_IsScaling)
{
var distance = this.Distance(e.GetX(0), e.GetX(1), e.GetY(0), e.GetY(1));
var scale = (distance - m_PreviousDistance) / this.DispDistance();
m_PreviousDistance = distance;
scale += 1;
scale = scale * scale;
this.ZoomTo(scale, m_Width / 2, m_Height / 2);
this.Cutting();
}
else if (!m_IsScaling)
{
var distanceX = m_PreviousMoveX - (int)e.GetX();
var distanceY = m_PreviousMoveY - (int)e.GetY();
m_PreviousMoveX = (int)e.GetX();
m_PreviousMoveY = (int)e.GetY();
m_Matrix.PostTranslate(-distanceX, -distanceY);
this.Cutting();
}
}
break;
case MotionEventActions.Up:
case MotionEventActions.Pointer1Up:
case MotionEventActions.Pointer2Up:
{
if (touchCount <= 1)
{
m_IsScaling = false;
}
}
break;
}
return true;
}
public bool OnTouch(View v, MotionEvent e)
{
return OnTouchEvent(e);
}
}
}