Develop Reference

Want to map zoomed image coordinates with actual image coordinates in android imageview

I am currently using this gitup touchimageview https://github.com/MikeOrtiz/TouchImageView library.... After zoom,based on the zoom percentage I want to map the longpress coordinates to original image coordinates. Any help will be appreciated

Try to get matrix of ImageView:
float[] values = new float[9];
getImageMatrix().getValues(values);
With this array, you have position of top-left corner in terms of image on indexes 2 and 5. For example, when values[2], values[5] is -10,-10 it means, that left top corner of screen is 10,10 pixel of image. So, you can get coordinate of long press:
float imageX = (pressX - values[2])/scale;
float imageY = (pressY - values[5])/scale;
Recently I work with zoomed images, and use this library: https://github.com/chrisbanes/PhotoView
I think its a bit better, it have some predifined touches with image coordinates, and is still improved (last commit ~2 months ago)

Android view 3d rotate transformation on big resolution screens

I'm implementing 3d card flip animation for android (api > 14) and have an issue with big screen tablets (> 2048 dpi). During problem investigation i've come to the following basic block:
Tried to just transform a view (simple ImageView) using matrix and rotateY of camera by some angle and it works ok for angle < 60 and angle > 120 (transformed and displayed) but image disappears (just not displayed) when angle is between 60 and 120. Here is the code I use:
private void applyTransform(float degree)
{
float [] values = {1.0f, 0.0f, 0.0f, 0.0f, 1.0f, 0.0f, 0.0f, 0.0f, 1.0f};
float centerX = image1.getMeasuredWidth() / 2.0f;
float centerY = image1.getMeasuredHeight() / 2.0f;
Matrix m = new Matrix();
m.setValues(values);
Camera camera = new Camera();
camera.save();
camera.rotateY(degree);
camera.getMatrix(m);
camera.restore();
m.preTranslate(-centerX, -centerY); // 1 draws fine without these 2 lines
m.postTranslate(centerX, centerY); // 2
image1.setImageMatrix(m);
}
And here is my layout XML
<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent">
<ImageView
android:id="#+id/ImageView01"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:src="#drawable/naponer"
android:clickable="true"
android:scaleType="matrix">
</ImageView>
</FrameLayout>
So I have the following cases:
works fine for any angle, any center point if running on small screens 800X480, 1024x720, etc...
works ok for angle < 60 and > 120 when running on big screen devices 2048x1536, 2560x1600...
works ok for any angle on any device if rotation not centered (matrix pre and post translations commented out )
fails (image disappears) when running on big screen device, rotation centered and angle is between 60 and 120 degrees.
Please tell what I'm doing wrong and advise some workaround... thank you!!!

This problem is caused by the camera distance used to calculate the transformation. While the Camera class itself doesn't say much about the subject, it is better explained in the documentation for the View.setCameraDistance() method (emphasis mine):
Sets the distance along the Z axis (orthogonal to the X/Y plane on
which views are drawn) from the camera to this view. The camera's
distance affects 3D transformations, for instance rotations around the
X and Y axis. (...)
The distance of the camera from the view plane can have an affect on
the perspective distortion of the view when it is rotated around the x
or y axis. For example, a large distance will result in a large
viewing angle, and there will not be much perspective distortion of
the view as it rotates. A short distance may cause much more
perspective distortion upon rotation, and can also result in some
drawing artifacts if the rotated view ends up partially behind the
camera (which is why the recommendation is to use a distance at
least as far as the size of the view, if the view is to be rotated.)
To be honest, I hadn't seen this particular effect (not drawing at all) before, but I suspected it could be related to this question related to perspective distortion I'd encountered in the past. :)
Therefore, the solution is to use the Camera.setLocation() method to ensure this doesn't happen.
An important distinction with the View.setCameraDistance() method is that the units are not the same, since setLocation() doesn't use pixels. While setCameraDistance() adjusts for density, setLocation() does not. Therefore, if you wanted to calculate an appropriate z-distance based on the view's dimensions, remember to adjust for density. For example:
float cameraDistance = Math.max(image1.getMeasuredHeight(), image1.getMeasuredWidth()) * 5;
float densityDpi = getResources().getDisplayMetrics().densityDpi;
camera.setLocation(0, 0, -cameraDistance / densityDpi);

Instead of using 12 lines to create rotation matrix, you could just implement this one in first line http://en.wikipedia.org/wiki/Rotation_matrix
Depending of effect you want, you might want to center image to axis you want to rotate around.
http://en.wikipedia.org/wiki/Transformation_matrix
Hmm for image disappearing, I would guess it has something to do with either memory (out of memory - although this would bring exception) or rounding problems. Maybe you could try increasing precision to double precision?
One thing that comes to mind is that cos(alpha) goes toward 0 when alpha goes toward PI/2. Other than that I don's see any correlation between angles and why it doesn't work for big images.

You need to adjust your Translate coordinates. When calculating the translation for your image you need to take image size into account too. When you perform matrix calculations you set android:scaleType="matrix" for your ImageView. This aligns your image at the top left corner by default. Then, when you apply your pre/post translation, your image may get off the bounds of your ImageView (especially if the ImageView is relatively large and your image is relatively small, like in case of beeg screen tablets).
The following translation results in the image being rotated around its center Y axis and keeps the image aligned to the top left corner:
m.preTranslate(-imageWidth/2, 0);
m.postTranslate(imageWidth/2, 0);
The following alternative results in the image being rotated around its center Y/X axises and aligns the image to the center of the ImageView:
m.preTranslate(-imageWidth/2, -imageHeight/2);
m.postTranslate(centerX, centerY);
If your image is a bitmap you can use intrinsic width/height:
Drawable drawable = image1.getDrawable();
imageHeight = drawable.getIntrinsicHeight();
imageWidth = drawable.getIntrinsicWidth();

Rotate a Scaled Image From the Center

I have some sprites (Well, custom classes that implement Sprite, but whatever) that I resize. AndEngine resizes the image from the center, which makes an image placed at 0,0 no longer appear at 0,0. To fix this I applied
sprite.setScaleCenterX(0);
sprite.setScaleCenterY(0);
This places the image where I want it. However, now when I rotate the image, the image moves around (If the image were a plain square, rotating it should make no visible change). To fix this I applied
sprite.setRotationCenterX((sprite.getWidth() * sprite.getScaleX()) / 2);
sprite.setRotationCenterY((sprite.getHeight() * sprite.getScaleY()) / 2);
(For some reason, resizing a Sprite doesn't change the dimensions of the sprite, just the visual image, hence multiplying it by the scale). This, however, did not correct the problem, but merely changed where the image moved to when flipped.
Is my math off here? Wouldn't this center the rotation on the image so that the image doesn't move position? Or is there something else I'm missing?
Below is full code:
Sprite sprite = new Sprite(0, 0, singleTrackTR, getVertexBufferObjectManager());
sprite.setScale(scaleX, scaleY);
sprite.setScaleCenterX(0);
sprite.setScaleCenterY(0);
sprite.setRotationCenterX((sprite.getWidth() * sprite.getScaleX()) / 2);
sprite.setRotationCenterY((sprite.getHeight() * sprite.getScaleY()) / 2);

All your code is correct. I tried it myself, both the setProperty(x, y) and the setPropertyX/Y(a) versions.
By any chance, do you have it connected to a Body? Note that the Body also doesn't scale with a Sprite's setScale. It has its own setTransform method, which takes x and y (that you both have to divide by PhysicsConstants.PIXEL_TO_METER_RATIO_DEFAULT) and a rotation value.

Android - Rotate image around center point?

How can I rotate a bitmap (not a view or canvas) around its center point when the user touches it and drags it?
I have tried loads of examples on stack overflow and none appear to work.
So far I have:
double r = Math.atan2(posX - dial.getWidth() / 2, dial.getHeight() / 2 - posY);
rotation = (int) Math.toDegrees(r);

Create Matrix then set rotate via setRotate(degrees). Then use this matrix when creating new Bitmap: Bitmap.createBitmap(..)

Rotate image along with touch to fix point in android

I am trying to rotate image in image view coresponding with touch to fix pivote pint of image . i have seen many of example but i dont clear with all of it .somebody have idea ..how can do it this this ?

Since there is no code or details provided about where the bitmap is drawn i assume its at the center of the screen. You can rotate the canvas on center point like this
double rotationAngleRadians = Math.atan2(currentX - centerX, centerY - currentY);
rotationAngleDegrees = (int) Math.toDegrees(rotationAngleRadians );
canvas.rotate(rotationAngleDegrees , centerX, centerY);