I'm implementing a zoomable View from examples I've found on Stack and other websites. I do want to add a drawing feature to the view. I'm able to get the paths to show up but the scaling is way off from the image behind it. I used an example android image where I traced along the shape and the paths appeared to the left and above it. Also, zooming causes it to shift (pictures below).
I've been playing around with the onDraw method where the canvas is drawn but with little success. I basically use a switch whether the onTouch responds to shifting/zooming or drawing the paths.
protected void onDraw(Canvas canvas) {
if(imgBitmap != null && canvas != null)
{
canvas.drawBitmap(imgBitmap, matrix, background);
canvas.setMatrix(matrix);
for (int i = 0; i < colors.size(); i++) {
canvas.drawPath(paths.get(i), colors.get(i));
}
canvas.drawPath(drawPath, drawPaint);
}
}
Here are the pictures and rest of code below:
public class ZoomImage extends View {
private static final String TAG = "ZoomableImageView";
private Bitmap imgBitmap = null;
private int containerWidth;
private int containerHeight;
Paint background;
//Matrices will be used to move and zoom image
Matrix matrix = new Matrix();
Matrix savedMatrix = new Matrix();
PointF start = new PointF();
float currentScale;
float curX;
float curY;
//We can be in one of these 3 states
static final int NONE = 0;
static final int DRAG = 1;
static final int ZOOM = 2;
int mode = NONE;
//For animating stuff
float targetX;
float targetY;
float targetScale;
float targetScaleX;
float targetScaleY;
float scaleChange;
float targetRatio;
float transitionalRatio;
float easing = 0.2f;
boolean isAnimating = false;
float scaleDampingFactor = 0.5f;
//For pinch and zoom
float oldDist = 1f;
PointF mid = new PointF();
private Handler mHandler = new Handler();
float minScale;
float maxScale = 3.0f;
float wpRadius = 25.0f;
float wpInnerRadius = 20.0f;
float screenDensity;
private GestureDetector gestureDetector;
public static final int DEFAULT_SCALE_FIT_INSIDE = 0;
public static final int DEFAULT_SCALE_ORIGINAL = 1;
private int defaultScale;
// Drawing path
private Path drawPath;
// Drawing and canvas paint
public Paint drawPaint;
// Canvas
private Canvas drawCanvas;
// Canvas bitmap
private Bitmap canvasBitmap;
// Counts how many fingers are on the screen
int pointerCount;
// Detects pinch to zoom activity
// Bounds used to draw paths when zoomed in
Rect clipBounds;
// List of saved paths
public ArrayList<Path> paths = new ArrayList<Path>();
// List of saved colors
public ArrayList<Paint> colors = new ArrayList<Paint>();
// Creates Path and Paint for drawing
public void setUpDrawing() {
System.out.println("--setUpDrawing--");
drawPath = new Path();
drawPaint = new Paint();
drawPaint.setColor(Color.RED);
drawPaint.setAntiAlias(true);
drawPaint.setStrokeWidth(8);
drawPaint.setStyle(Paint.Style.STROKE);
drawPaint.setStrokeJoin(Paint.Join.ROUND);
drawPaint.setStrokeCap(Paint.Cap.ROUND);
}
public int getDefaultScale() {
return defaultScale;
}
public void setDefaultScale(int defaultScale) {
this.defaultScale = defaultScale;
}
public ZoomImage(Context context) {
super(context);
setFocusable(true);
setFocusableInTouchMode(true);
screenDensity = context.getResources().getDisplayMetrics().density;
initPaints();
gestureDetector = new GestureDetector(new MyGestureDetector());
setUpDrawing();
}
public ZoomImage(Context context, AttributeSet attrs) {
super(context, attrs);
screenDensity = context.getResources().getDisplayMetrics().density;
initPaints();
gestureDetector = new GestureDetector(new MyGestureDetector());
defaultScale = ZoomImage.DEFAULT_SCALE_FIT_INSIDE;
setUpDrawing();
}
private void initPaints() {
background = new Paint();
setUpDrawing();
}
@Override
protected void onSizeChanged(int width, int height, int oldWidth, int oldHeight) {
super.onSizeChanged(width, height, oldWidth, oldHeight);
//Reset the width and height. Will draw bitmap and change
containerWidth = width;
containerHeight = height;
if(imgBitmap != null) {
drawCanvas = new Canvas(imgBitmap);
int imgHeight = imgBitmap.getHeight();
int imgWidth = imgBitmap.getWidth();
float scale;
int initX = 0;
int initY = 0;
if(defaultScale == ZoomImage.DEFAULT_SCALE_FIT_INSIDE) {
if(imgWidth > containerWidth) {
scale = (float)containerWidth / imgWidth;
float newHeight = imgHeight * scale;
initY = (containerHeight - (int)newHeight)/2;
matrix.setScale(scale, scale);
matrix.postTranslate(0, initY);
}
else {
scale = (float)containerHeight / imgHeight;
float newWidth = imgWidth * scale;
initX = (containerWidth - (int)newWidth)/2;
matrix.setScale(scale, scale);
matrix.postTranslate(initX, 0);
}
curX = initX;
curY = initY;
currentScale = scale;
minScale = scale;
}
else {
if(imgWidth > containerWidth) {
initY = (containerHeight - (int)imgHeight)/2;
matrix.postTranslate(0, initY);
}
else {
initX = (containerWidth - (int)imgWidth)/2;
matrix.postTranslate(initX, 0);
}
curX = initX;
curY = initY;
currentScale = 1.0f;
minScale = 1.0f;
}
invalidate();
}
}
@Override
protected void onDraw(Canvas canvas) {
if(imgBitmap != null && canvas != null)
{
canvas.drawBitmap(imgBitmap, matrix, background);
canvas.setMatrix(matrix);
for (int i = 0; i < colors.size(); i++) {
canvas.drawPath(paths.get(i), colors.get(i));
}
canvas.drawPath(drawPath, drawPaint);
}
}
public void reDrawUndo() {
System.out.println("paths.size" + paths.size());
if (paths.size() > 0) {
paths.remove(paths.size() - 1);
colors.remove(colors.size() - 1);
invalidate();
}
}
//Checks and sets the target image x and y co-ordinates if out of bounds
private void checkImageConstraints() {
if(imgBitmap == null) {
return;
}
float[] mvals = new float[9];
matrix.getValues(mvals);
currentScale = mvals[0];
if(currentScale < minScale) {
float deltaScale = minScale / currentScale;
float px = containerWidth/2;
float py = containerHeight/2;
matrix.postScale(deltaScale, deltaScale, px, py);
invalidate();
}
matrix.getValues(mvals);
currentScale = mvals[0];
curX = mvals[2];
curY = mvals[5];
int rangeLimitX = containerWidth - (int)(imgBitmap.getWidth() * currentScale);
int rangeLimitY = containerHeight - (int)(imgBitmap.getHeight() * currentScale);
boolean toMoveX = false;
boolean toMoveY = false;
if(rangeLimitX < 0) {
if(curX > 0) {
targetX = 0;
toMoveX = true;
}
else if(curX < rangeLimitX) {
targetX = rangeLimitX;
toMoveX = true;
}
}
else {
targetX = rangeLimitX / 2;
toMoveX = true;
}
if(rangeLimitY < 0) {
if(curY > 0) {
targetY = 0;
toMoveY = true;
}
else if(curY < rangeLimitY) {
targetY = rangeLimitY;
toMoveY = true;
}
}
else {
targetY = rangeLimitY / 2;
toMoveY = true;
}
if(toMoveX == true || toMoveY == true) {
if(toMoveY == false) {
targetY = curY;
}
if(toMoveX == false) {
targetX = curX;
}
//Disable touch event actions
isAnimating = true;
//Initialize timer
mHandler.removeCallbacks(mUpdateImagePositionTask);
mHandler.postDelayed(mUpdateImagePositionTask, 100);
}
}
@Override
public boolean onTouchEvent(MotionEvent event) {
float touchX = event.getX();
System.out.println("touchX: " + event.getX());
float touchY = event.getY();
System.out.println("touchY: " + event.getY());
// Is drawing mode on?
if (Deal.on){
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
drawPath.moveTo(touchX, touchY);
break;
case MotionEvent.ACTION_MOVE:
drawPath.lineTo(touchX, touchY);
break;
case MotionEvent.ACTION_UP:
Paint newPaint = new Paint();
newPaint.set(drawPaint);
colors.add(newPaint);
paths.add(drawPath);
drawPath = new Path();
drawPath.reset();
break;
case MotionEvent.ACTION_POINTER_DOWN:
System.out.println("bleh");
break;
default:
return false;
}
}
else {
if(gestureDetector.onTouchEvent(event)) {
return true;
}
if(isAnimating == true) {
return true;
}
//Handle touch events here
float[] mvals = new float[9];
switch(event.getAction() & MotionEvent.ACTION_MASK) {
case MotionEvent.ACTION_DOWN:
if(isAnimating == false) {
savedMatrix.set(matrix);
start.set(event.getX(), event.getY());
mode = DRAG;
}
break;
case MotionEvent.ACTION_POINTER_DOWN:
oldDist = spacing(event);
if(oldDist > 10f) {
savedMatrix.set(matrix);
midPoint(mid, event);
mode = ZOOM;
}
break;
case MotionEvent.ACTION_UP:
case MotionEvent.ACTION_POINTER_UP:
mode = NONE;
matrix.getValues(mvals);
curX = mvals[2];
curY = mvals[5];
currentScale = mvals[0];
if(isAnimating == false) {
checkImageConstraints();
}
break;
case MotionEvent.ACTION_MOVE:
if(mode == DRAG && isAnimating == false) {
matrix.set(savedMatrix);
float diffX = event.getX() - start.x;
float diffY = event.getY() - start.y;
matrix.postTranslate(diffX, diffY);
matrix.getValues(mvals);
curX = mvals[2];
curY = mvals[5];
currentScale = mvals[0];
}
else if(mode == ZOOM && isAnimating == false) {
float newDist = spacing(event);
if(newDist > 10f) {
matrix.set(savedMatrix);
float scale = newDist / oldDist;
matrix.getValues(mvals);
currentScale = mvals[0];
if(currentScale * scale <= minScale) {
matrix.postScale(minScale/currentScale, minScale/currentScale, mid.x, mid.y);
}
else if(currentScale * scale >= maxScale) {
matrix.postScale(maxScale/currentScale, maxScale/currentScale, mid.x, mid.y);
}
else {
matrix.postScale(scale, scale, mid.x, mid.y);
}
matrix.getValues(mvals);
curX = mvals[2];
curY = mvals[5];
currentScale = mvals[0];
}
}
break;
}
}
//Calculate the transformations and then invalidate
invalidate();
return true;
}
private float spacing(MotionEvent event) {
float x = event.getX(0) - event.getX(1);
float y = event.getY(0) - event.getY(1);
return FloatMath.sqrt(x * x + y * y);
}
private void midPoint(PointF point, MotionEvent event) {
float x = event.getX(0) + event.getX(1);
float y = event.getY(0) + event.getY(1);
point.set(x/2, y/2);
}
public void setImageBitmap(Bitmap b) {
if(b != null) {
imgBitmap = b;
containerWidth = getWidth();
containerHeight = getHeight();
int imgHeight = imgBitmap.getHeight();
int imgWidth = imgBitmap.getWidth();
float scale;
int initX = 0;
int initY = 0;
matrix.reset();
if(defaultScale == ZoomImage.DEFAULT_SCALE_FIT_INSIDE) {
if(imgWidth > containerWidth) {
scale = (float)containerWidth / imgWidth;
float newHeight = imgHeight * scale;
initY = (containerHeight - (int)newHeight)/2;
matrix.setScale(scale, scale);
matrix.postTranslate(0, initY);
}
else {
scale = (float)containerHeight / imgHeight;
float newWidth = imgWidth * scale;
initX = (containerWidth - (int)newWidth)/2;
matrix.setScale(scale, scale);
matrix.postTranslate(initX, 0);
}
curX = initX;
curY = initY;
currentScale = scale;
minScale = scale;
}
else {
if(imgWidth > containerWidth) {
initX = 0;
if(imgHeight > containerHeight) {
initY = 0;
}
else {
initY = (containerHeight - (int)imgHeight)/2;
}
matrix.postTranslate(0, initY);
}
else {
initX = (containerWidth - (int)imgWidth)/2;
if(imgHeight > containerHeight) {
initY = 0;
}
else {
initY = (containerHeight - (int)imgHeight)/2;
}
matrix.postTranslate(initX, 0);
}
curX = initX;
curY = initY;
currentScale = 1.0f;
minScale = 1.0f;
}
invalidate();
}
else {
Log.d(TAG, "bitmap is null");
}
}
public Bitmap getPhotoBitmap() {
return imgBitmap;
}
private Runnable mUpdateImagePositionTask = new Runnable() {
public void run() {
float[] mvals;
if(Math.abs(targetX - curX) < 5 && Math.abs(targetY - curY) < 5) {
isAnimating = false;
mHandler.removeCallbacks(mUpdateImagePositionTask);
mvals = new float[9];
matrix.getValues(mvals);
currentScale = mvals[0];
curX = mvals[2];
curY = mvals[5];
//Set the image parameters and invalidate display
float diffX = (targetX - curX);
float diffY = (targetY - curY);
matrix.postTranslate(diffX, diffY);
}
else {
isAnimating = true;
mvals = new float[9];
matrix.getValues(mvals);
currentScale = mvals[0];
curX = mvals[2];
curY = mvals[5];
//Set the image parameters and invalidate display
float diffX = (targetX - curX) * 0.3f;
float diffY = (targetY - curY) * 0.3f;
matrix.postTranslate(diffX, diffY);
mHandler.postDelayed(this, 25);
}
invalidate();
}
};
private Runnable mUpdateImageScale = new Runnable() {
public void run() {
float transitionalRatio = targetScale / currentScale;
float dx;
if(Math.abs(transitionalRatio - 1) > 0.05) {
isAnimating = true;
if(targetScale > currentScale) {
dx = transitionalRatio - 1;
scaleChange = 1 + dx * 0.2f;
currentScale *= scaleChange;
if(currentScale > targetScale) {
currentScale = currentScale / scaleChange;
scaleChange = 1;
}
}
else {
dx = 1 - transitionalRatio;
scaleChange = 1 - dx * 0.5f;
currentScale *= scaleChange;
if(currentScale < targetScale) {
currentScale = currentScale / scaleChange;
scaleChange = 1;
}
}
if(scaleChange != 1) {
matrix.postScale(scaleChange, scaleChange, targetScaleX, targetScaleY);
mHandler.postDelayed(mUpdateImageScale, 15);
invalidate();
}
else {
isAnimating = false;
scaleChange = 1;
matrix.postScale(targetScale/currentScale, targetScale/currentScale, targetScaleX, targetScaleY);
currentScale = targetScale;
mHandler.removeCallbacks(mUpdateImageScale);
invalidate();
checkImageConstraints();
}
}
else {
isAnimating = false;
scaleChange = 1;
matrix.postScale(targetScale/currentScale, targetScale/currentScale, targetScaleX, targetScaleY);
currentScale = targetScale;
mHandler.removeCallbacks(mUpdateImageScale);
invalidate();
checkImageConstraints();
}
}
};
class MyGestureDetector extends SimpleOnGestureListener {
@Override
public boolean onDoubleTap(MotionEvent event) {
if(isAnimating == true) {
return true;
}
scaleChange = 1;
isAnimating = true;
targetScaleX = event.getX();
targetScaleY = event.getY();
if(Math.abs(currentScale - maxScale) > 0.1) {
targetScale = maxScale;
}
else {
targetScale = minScale;
}
targetRatio = targetScale / currentScale;
mHandler.removeCallbacks(mUpdateImageScale);
mHandler.post(mUpdateImageScale);
return true;
}
@Override
public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
return super.onFling(e1, e2, velocityX, velocityY);
}
@Override
public boolean onDown(MotionEvent e) {
return false;
}
}
}
EDIT:
Adding canvas.concat(matrix) fixed the zooming. Still trying to fix the offset...
onDraw changed to:
super.onDraw(canvas);
canvas.save();
if(imgBitmap != null && canvas != null){
if(drawCanvas == null)
drawCanvas = new Canvas(imgBitmap);
clipBounds = canvas.getClipBounds();
canvas.drawBitmap(imgBitmap, matrix, background);
canvas.concat(matrix);
for (int i = 0; i < colors.size(); i++) {
canvas.drawPath(paths.get(i), colors.get(i));
}
canvas.drawPath(drawPath, drawPaint);
}
canvas.restore();
invalidate();
Got it! Get the matrix values for scale and offset and adjust the touchX and touchY accordingly. mv[4] is the scale, while mv[2] and mv[5] are the offsets in x and y, respectively.
float[] mv = new float[9];
@Override
public boolean onTouchEvent(MotionEvent event) {
// Get the values from the matrix into the float array
matrix.getValues(mv);
float touchX = (event.getX()*(1/mv[4]) - (mv[2]/mv[4]));
float touchY = (event.getY()*(1/mv[4]) - (mv[5]/mv[4]));
来源：https://stackoverflow.com/questions/20006428/zoomview-canvas-matrix-android