Develop Reference

Android Canvas matrix

For a school project I need to make a module to shrink a bitmap. So I made a matrix for this but when I draw directly the bitmap with the matrix like this :
canvas.drawBitmap(Bmp, ShrinkMatrice, p);
This work very fine, but I need to assign this matrix into the Bmp so I used a second canvas like this :
Canvas SuperCanvas = new Canvas(Bmp);
SuperCanvas.drawBitmap(Bmp, ShrinkMatrice, p);
but when I look the result with this :
canvas.drawBitmap(Bmp, 0,0, p);
the result look like this ( see the picture on the link ), the rest of the page is not draw correctly ...
if someone can explain me this problem :/...
Thank you in advance...
(Sorry if I made some error it's my first time on stackoverflow )

Android: Rotating large image crashes without throwing an error

I have searched and found simple code to rotate an image. I am pulling the image out of an ImageView object into a bitmap, rotating it then putting it back. I realize this is not the most effective method but I don't think it should crash without giving an error message in the CATCH block.
Here is my code. The only value passed in is "r" or "l" depending on which direction I want to rotate. Smaler images (1500x1500 or smaller) work just fine. Things go bad around the 2500x2500 size.
public void rotate(String dir)
{
try
{
float angle = (dir.equals("r") ? 90 : -90);
Bitmap bitmap = ((BitmapDrawable) imageView.getDrawable()).getBitmap();
Matrix matrix = new Matrix();
matrix.reset();
matrix.postRotate(angle);
bitmap = Bitmap.createBitmap(bitmap, 0, 0, bitmap.getWidth(), bitmap.getHeight(), matrix, false);
imageView.setImageBitmap(bitmap);
}
catch(Exception e)
{
Utilities.logError(e.toString());
}
}
Any clue as to why it is crashing and why it doesn't thow an exception? I just get a message "Unfortuantly process .... has stopped" and I get kicked back to the welcome screen of my app.
Oh, for kicks I set the angle to ZERO (hard coded) and it didn't crash. I suspect that it is just taking too long to rotate and Android is having a fit. But I am not sure how to confirm that as the problem or how to tell Android to wait a little longer.
Even if I reduce the preview image for the rotation, when I go to save I will have to rotate the full size image at least once and will hit this same issue. Won't I?

I can more or less guarantee without looking at the logs that you're getting an Out Of Memory Exception.
You need to use smaller images, or use a different method to rotate that doesn't use up so much memory (you're allocating 2 2500x2500 bitmaps at the same time here! that's tons!).
Try using a RotateAnimation to get your effect instead.
Hope this helps :)

Rotating an image bitmap with animation android

In my app I am giving a functionality to edit an image from the filepath.
Now I want to add a feature to change the image orientation with animation and then save it.
I am able to change the orientation but don't know how to add animation to it.
Here's my code.
ImageView img;
Bitmap bmp;
Bitmap rotatedBMP;
String imageFilePath="";
File imgFile;
public void rotate(){
if(rotatedBMP == null){
if(imgFile != null && imgFile.exists())
bmp = BitmapFactory.decodeFile(imgFile.getAbsolutePath());
}else
bmp = rotatedBMP;
// Getting width & height of the given image.
int w = bmp.getWidth();
int h = bmp.getHeight();
Matrix mtx = new Matrix();
mtx.preRotate(90);
rotatedBMP = Bitmap.createBitmap(bmp, 0, 0, w, h, mtx, true);
/*BitmapDrawable bmd = new BitmapDrawable(rotatedBMP);
img.setImageDrawable(bmd);*/
img.setImageBitmap(rotatedBMP);
}

There's a conflict between your desire to animate rotate a view, and your desire to rotate and save the actual bitmap.
If you want to rotate the image view, the good way to do that is to rotate the canvas in an onDraw method with an animation update step, or to use Android's helper for that like RotateAnimation. Drop us a comment if you want examples.
That's the "good way" because it doesn't create a new bitmap on every animation frame, which would be very expensive.
However, you've got a conflict that you also want to rotate the bitmap itself, rather than just the view, so as to save it. This is fine given it's not on every animation step.
You consequently will have to save the user's chosen transformations you want to apply to the bitmap as late as possible. Then animate the view however is appropriate in response to the user. On the save, you'd concat all the users transformations on writing to the file. Or give up on the idea of animating it.
My implementation idea would be to store a second matrix locally and have each user input both update the canvas transforms and that matrix. You'd then 'get hold' of the bitmap as it were when the save button is pressed and apply it to the updated transformation matrix.
Happy to elaborate as requested.
Some sources
Android: Rotate image in imageview by an angle (mentions issues with creating many bitmaps too)
Rotating a view in Android (gauravjain0102's answer is underrated!)

AndroidPlot: How to render a chart in an AppWidget?

I'm trying to use AndroidPlot to draw a chart in a homescreen widget.
I know that in a normal app, it uses a custom view and from what I've seen (Android: AppWidget with custom view not working), the workaround is to render this as a bitmap in an imageView.
Now I've taken the quickstart code for AndroidPlot and put it into the provider class but it doesn't seem to render anything when I drop it on the homescreen.
The difference between this code and the original quickstart code is that in the quickstart, it leverages the Activity.findViewById but obviously it can't be used here.
Can anyone see something here that I'm doing wrong that may be causing the empty rendering?
Appreciate any help you could provide!
private Bitmap getChartImage(Context context)
{
// initialize our XYPlot reference:
mySimpleXYPlot = new XYPlot(context, "My Simple XYPlot");
mySimpleXYPlot.setDrawingCacheEnabled(true);
// add a new series
mySimpleXYPlot.addSeries(new SimpleXYSeries(), LineAndPointRenderer.class, new LineAndPointFormatter(Color.rgb(0, 200, 0), Color.rgb(200, 0, 0)));
// reduce the number of range labels
mySimpleXYPlot.getGraphWidget().setRangeTicksPerLabel(4);
// reposition the domain label to look a little cleaner:
Widget domainLabelWidget = mySimpleXYPlot.getDomainLabelWidget();
mySimpleXYPlot.position(domainLabelWidget, // the widget to position
45, // x position value, in this case 45 pixels
XLayoutStyle.ABSOLUTE_FROM_LEFT, // how the x position value is applied, in this case from the left
0, // y position value
YLayoutStyle.ABSOLUTE_FROM_BOTTOM, // how the y position is applied, in this case from the bottom
AnchorPosition.LEFT_BOTTOM); // point to use as the origin of the widget being positioned
// get rid of the visual aids for positioning:
mySimpleXYPlot.disableAllMarkup();
//mySimpleXYPlot.measure(150, 150);
//mySimpleXYPlot.layout(0, 0, 150, 150);
Bitmap bmp = mySimpleXYPlot.getDrawingCache();
return bmp;
}

Have you stepped through to see if the bitmap is actually empty? My guess is that the Bitmap is fine and the problem exists outside of this chunk of code. Take a look at this example usage of a widget with AndroidPlot - it's super minimal and it definitely works. Hopefully there's a solution in there for you :)
Nick

OutOfMemoryError: Android large Bitmap rotation (90°)

I have a big Memory Problem:
// in sourceImage is a big JPEG previously loaded
Matrix mat = new Matrix();
mat.postRotate(90);
Bitmap rotatedImage = Bitmap.createBitmap(sourceImage, 0, 0, sourceImage.getWidth(), sourceImage.getHeight(), mat, true);
Always i Run this code, my App crashes and says "VM won't let us allocate xxxxxx bytes"
Can you help me?
Edit:
I saw much similar questions here, but i don't know how to recycle the sourceImage before rotatating it... (cause the second instance is to big to hold it at the same time)
Thanks.

You can't create a new rotated bitmap without holding temporary 2 bitmaps in memory.
But you can display the bitmap rotated without creating a new bitmap (apply a transformation).
ImageView does not come with rotation capabilities, so you should write your own extended version of ImageView (RotatedImageView?).
The idea is to override the onDraw method with something like this (not tested).
#Override
public void onDraw(Canvas canvas) {
canvas.rotate((int)(angle * 180 / Math.PI), getWidth() >> 1, getHeight() >> 1);
super.onDraw(canvas);
}

For others like me:
there's an option to have the camera perform the rotation,
https://stackoverflow.com/a/16010289/755804