The set-methods will replace the current Matrix with new values, disregarding whatever the Matrix contained before. The pre and post method will apply a new transformation before or after whatever the current Matrix contains.

In this example, the rotation will be ignored since we are using the set method and the m will only contain a translation:

 &gt; Matrix m = new Matrix();
 &gt; 
 &gt; m.setRotate(90); 
 &gt;
 &gt; m.setTranslate(100, 100);


In this example, the final matrix will be a translation followed by a rotation:

&gt; Matrix m = new Matrix();
&gt;
&gt; m.setTranslate(100, 100);
&gt;
&gt; m.postRotate(90);

In the final example, the final matrix will be a rotation followed by a translation:

&gt; Matrix m = new Matrix();
&gt;
&gt; m.setTranslate(100, 100);
&gt;
&gt; m.preRotate(90);

There is some more information in this (rather lengthy) post:

http://www.satyakomatineni.com/akc/display?url=displaynoteimpurl&amp;ownerUserId=satya&amp;reportId=2898

Hope it helps.

I want to replace a substring (e.g. `@&quot;replace&quot;`) of an `NSAttributedString` with another `NSAttributedString`.

I am looking for an equivalent method to `NSString`&#39;s [`stringByReplacingOccurrencesOfString:withString:`](https://developer.apple.com/library/mac/documentation/Cocoa/Reference/Foundation/Classes/NSString_Class/Reference/NSString.html#//apple_ref/doc/uid/20000154-SW6) for `NSAttributedString`.

Replace substring of NSAttributedString with another NSAttributedString

Our code:

     describe &quot;GET show&quot; do
       it &quot;assigns the requested subcategory as @subcategory&quot; do
         subcategory = Subcategory.create! valid_attributes
         get :show, :id =&gt; subcategory.id.to_s
         assigns(:subcategory).should eq(subcategory)
       end
    
       it &quot;has a sort parameter in the url&quot; do
         subcategory = Subcategory.create! valid_attributes
         get :show, {:id =&gt; subcategory.id.to_s, :params =&gt; {:sort =&gt; &#39;title&#39;}}
         helper.params[:sort].should_not be_nil
       end
     end

I got the following error message: 

    1) SubcategoriesController GET show has a sort parameter in the url
        Failure/Error: helper.params[:sort].should_not be_nil
        NameError:
          undefined local variable or method `helper&#39; for #&lt;RSpec::Core::ExampleGroup::Nested_4::Nested_2:0x007f81a467c848&gt;
        # ./spec/controllers/subcategories_controller_spec.rb:54:in `block (3 levels) in &lt;top (required)&gt;&#39;

How can I test params in rspec?

how to test params passed into a controller in rails 3, using rspec?

The [documentation][1] is pretty vague as to what is actually happening when these methods are used.  Can someone explain how Matrix actually affects the Bitmap that it&#39;s being set to? They use the term concatenate in there, but I&#39;m unclear on how that term applies to coordinate data (having only used it in regard to string manipulation before).


  [1]: http://developer.android.com/reference/android/graphics/Matrix.html

Looking for an explanation of post/pre/set Translate (in Matrix object) and how to use them

<p>The <a href="http://developer.android.com/reference/android/graphics/Matrix.html" target="_blank" rel="noopener noreferrer">documentation</a> is pretty vague as to what is actually happening when these methods are used.  Can someone explain how Matrix actually affects the Bitmap that it's being set to? They use the term concatenate in there, but I'm unclear on how that term applies to coordinate data (having only used it in regard to string manipulation before).</p>


Which is the simplest method to get html code from a webview?
I have tried several methods from stackoverflow and google, but can&#39;t find an exact method. Please mention an exact way.




    public class htmldecoder extends Activity implements OnClickListener,TextWatcher
    {
	TextView txturl;
	Button btgo;
	WebView wvbrowser;
	TextView txtcode;
	ImageButton btcode;
	LinearLayout llayout;
	int flagbtcode;
	public void onCreate(Bundle savedInstanceState)
	{
		        super.onCreate(savedInstanceState);
		            setContentView(R.layout.htmldecoder);
	  
		txturl=(TextView)findViewById(R.id.txturl);
		
		btgo=(Button)findViewById(R.id.btgo);
		btgo.setOnClickListener(this);
		
		wvbrowser=(WebView)findViewById(R.id.wvbrowser);
		wvbrowser.setWebViewClient(new HelloWebViewClient());
		wvbrowser.getSettings().setJavaScriptEnabled(true);
		wvbrowser.getSettings().setPluginsEnabled(true);
		wvbrowser.getSettings().setJavaScriptCanOpenWindowsAutomatically(true);
		wvbrowser.addJavascriptInterface(new MyJavaScriptInterface(),&quot;HTMLOUT&quot;);
		//wvbrowser.loadUrl(&quot;http://www.google.com&quot;);
		wvbrowser.loadUrl(&quot;javascript:window.HTMLOUT.showHTML(&#39;&lt;html&gt;&#39;+document.getElementsByTagName(&#39;html&#39;)[0].innerHTML+&#39;&lt;/html&gt;&#39;);&quot;);
		
		
		txtcode=(TextView)findViewById(R.id.txtcode);
		txtcode.addTextChangedListener(this);
		
		btcode=(ImageButton)findViewById(R.id.btcode);
		btcode.setOnClickListener(this);
		
		}

	public void onClick(View v)
	{
		if(btgo==v)
		{
			String url=txturl.getText().toString();
			if(!txturl.getText().toString().contains(&quot;http://&quot;))
	    	{
	    		url=&quot;http://&quot;+url;
	    	}
			wvbrowser.loadUrl(url);
			//wvbrowser.loadData(&quot;&lt;html&gt;&lt;head&gt;&lt;/head&gt;&lt;body&gt;&lt;div style=&#39;width:100px;height:100px;border:1px red solid;&#39;&gt;&lt;/div&gt;&lt;/body&gt;&lt;/html&gt;&quot;,&quot;text/html&quot;,&quot;utf-8&quot;);
		}
		else if(btcode==v)
		{
			ViewGroup.LayoutParams params1=wvbrowser.getLayoutParams();
			ViewGroup.LayoutParams params2=txtcode.getLayoutParams();
			if(flagbtcode==1)
			{
				params1.height=200;
				params2.height=220;
				flagbtcode=0;
				//txtcode.setText(wvbrowser.getContentDescription());
			}
			else
			{
				params1.height=420;
				params2.height=0;
				flagbtcode=1;
			}
			wvbrowser.setLayoutParams(params1);
			txtcode.setLayoutParams(params2);
			
		}
	}

	public class HelloWebViewClient extends WebViewClient {
	    @Override
	    public boolean shouldOverrideUrlLoading(WebView view, String url) {
	    	
	        view.loadUrl(url);
	        return true;
	    }
	    /*@Override
	    public void onPageFinished(WebView view, String url)
	    {
	        // This call inject JavaScript into the page which just finished loading. 
	        wvbrowser.loadUrl(&quot;javascript:window.HTMLOUT.processHTML(&#39;&lt;head&gt;&#39;+document.getElementsByTagName(&#39;html&#39;)[0].innerHTML+&#39;&lt;/head&gt;&#39;);&quot;);
	    }*/

	}
	class MyJavaScriptInterface
	{
		@SuppressWarnings(&quot;unused&quot;)
		public void showHTML(String html)
		{
		
			txtcode.setText(html);
		}
	}

	public void afterTextChanged(Editable s) {
		// TODO Auto-generated method stub
		
	}

	public void beforeTextChanged(CharSequence s, int start, int count,
			int after) {
		// TODO Auto-generated method stub
		
	}

	public void onTextChanged(CharSequence s, int start, int before, int count) {
		wvbrowser.loadData(&quot;&lt;html&gt;&lt;div&quot;+txtcode.getText().toString()+&quot;&gt;&lt;/div&gt;&lt;/html&gt;&quot;,&quot;text/html&quot;,&quot;utf-8&quot;);
		
	}
	
    }

how to get html content from a webview?

I have three files. The XML, the draw function and the main Activity.
I have some `LinearLayout` in my XML file.

    &lt;LinearLayout android:orientation=&quot;horizontal&quot;
                  android:layout_width=&quot;fill_parent&quot;
                  android:layout_height=&quot;fill_parent&quot;
                  android:layout_weight=&quot;1&quot;&gt;
        &lt;LinearLayout android:layout_width=&quot;fill_parent&quot;
                      android:layout_height=&quot;fill_parent&quot;
                      android:layout_weight=&quot;1&quot;
                      android:background=&quot;#ef3&quot;
                      android:id=&quot;@+id/img01&quot;/&gt;
        &lt;LinearLayout android:layout_width=&quot;fill_parent&quot;
                      android:layout_height=&quot;fill_parent&quot;
                      android:layout_weight=&quot;1&quot;
                      android:background=&quot;#E8A2B4&quot;
                      android:id=&quot;@+id/img02&quot;/&gt;
    &lt;/LinearLayout&gt;

This is the draw function:

    public class getBorder extends TextView {
        public getBorder(Context context) {
    	    super(context);
        }
    
        @Override
        protected void onDraw(Canvas canvas) {
            super.onDraw(canvas);
            Paint paint = new Paint();
    
            paint.setColor(android.graphics.Color.RED);
    
            canvas.drawLine(0, 0, this.getWidth() - 1, 0, paint);
            canvas.drawLine(0, 0, 0, this.getHeight() - 1, paint);
            canvas.drawLine(this.getWidth() - 1, 0, this.getWidth() - 1,
                this.getHeight() - 1, paint);
            canvas.drawLine(0, this.getHeight() - 1, this.getWidth() - 1,
                this.getHeight() - 1, paint);
    	}
    }

And this is the main Activity:

    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        final getBorder getBorder = new getBorder(this);
        final LinearLayout img01 = (LinearLayout) findViewById(R.id.img01);
        img01.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub
                getBorder.setWidth(100);
                getBorder.setHeight(100);
                img01.addView(getBorder);
            }
        });       
    }

The program could draw border but the size doesn&#39;t fit the `LinearLayout`. And when I click the `LinearLayout` again, the program crashed.

Also, I want to draw two circles in the center of the `LinearLayout`, but how could I figure out the center coordinates?

Android: how to draw a border to a LinearLayout

How can I get the context in a fragment?

I need to use my database whose constructor takes in the context, but `getApplicationContext()` and `FragmentClass.this` don&#39;t work so what can I do?

Database constructor

    public Database(Context ctx)
    {
        this.context = ctx;
        DBHelper = new DatabaseHelper(context);
    }


Using context in a fragment

How can I add a [placeholder][1] text to `EditText` in the class that isn&#39;t in the XML?

I have the following `EditText` in my code which will be shown in alertdialog:

		final EditText name = new EditText(this);

  [1]: https://developer.mozilla.org/en-US/docs/Web/HTML/Element/Input

Android add placeholder text to EditText

Is there a way to use the Android NumberPicker widget for choosing strings instead of integers?

Using NumberPicker Widget with Strings

The [Eigen][1] library can map existing memory into Eigen matrices.

    float array[3];
    Map&lt;Vector3f&gt;(array, 3).fill(10);
    int data[4] = 1, 2, 3, 4;
    Matrix2i mat2x2(data);
    MatrixXi mat2x2 = Map&lt;Matrix2i&gt;(data);
    MatrixXi mat2x2 = Map&lt;MatrixXi&gt;(data, 2, 2);

My question is, how can we get c array (e.g. float[] a) from eigen matrix (e.g. Matrix3f m)? What it the real layout of eigen matrix? Is the real data stored as in normal c array?


  [1]: http://eigen.tuxfamily.org/

Convert Eigen Matrix to C array

I&#39;m a physicist, and have been learning some programming, and have come across a lot of people using quaternions for rotations instead of writing things in matrix/vector form. 

In physics, there are very good reasons we don&#39;t use quaternions (despite the bizarre story that&#39;s occasionally told about Hamilton/Gibbs/etc). Physics requires that our descriptions have good analytic behavior (this has a precisely defined meaning, but in some rather technical ways that go far beyond what&#39;s taught in normal intro classes, so I won&#39;t go into any detail). It turns out that quaternions don&#39;t have this nice behavior, and so they aren&#39;t useful, and vectors/matrices do, so we use them.

However, restricted to rigid rotations and descriptions that do not use any analytic structures, 3D rotations can be equivalently described either way (or a few other ways).

Generally, we just want a mapping of a point X = (x, y, z) to a new point X&#39; = (x&#39;, y&#39;, z&#39;) subject to the constraint that X&lt;sup&gt;2&lt;/sup&gt; = X&#39;&lt;sup&gt;2&lt;/sup&gt;. And there are lots of things that do this. 

The naive way is to just draw the triangles this defines and use trigonometry, or use the isomorphism between a point (x, y, z) and a vector (x, y, z) and the function f(X) = X&#39; and a matrix MX = X&#39;, or using quaternions, or projecting out components of the old vector along the new one using some other method (x, y, z)&lt;sup&gt;T&lt;/sup&gt;.(a,b,c) (x&#39;,y&#39;,z&#39;), etc.

From a math point of view, these descriptions are all equivalent in this setting (as a theorem). They all have the same number of degrees of freedom, the same number of constraints, etc.

So why do quaternions seem to preferred over vectors?

The usual reasons I see are no gimbal lock, or numerical issues.

The no gimbal lock argument seems odd, since this is only a problem of euler angles. It is also only a coordinate problem (just like the singularity at r=0 in polar coordinates (the Jacobian looses rank)), which means it is only a local problem, and can be resolved by switching coordinates, rotating out of the degeneracy, or using two overlapping coordinate systems. 

I&#39;m less sure about numerical issues, since I don&#39;t know in detail how both of these (and any alternatives) would be implemented. I&#39;ve read that re-normalizing a quaternion is easier than doing that for a rotation matrix, but this is only true for a general matrix; a rotation has additional constraints that trivializes this (which are built into the definition of quaternions) (In fact, this has to be true since they have the same number of degrees of freedom). 

So what is the reason for the use of quaternions over vectors or other alternatives? 

Why are quaternions used for rotations?

I have a `data.frame` that looks like this.

    x a 1 
    x b 2 
    x c 3 
    y a 3 
    y b 3 
    y c 2 

I want this in matrix form so I can feed it to heatmap to make a plot.  The result should look something like:

        a    b    c
    x   1    2    3
    y   3    3    2

I have tried `cast` from the reshape package and I have tried writing a manual function to do this but I do not seem to be able to get it right.


Reshape three column data frame to matrix (&quot;long&quot; to &quot;wide&quot; format)

I have 92 set of data of same type.

I want to make a correlation matrix for any two combinations possible.

i.e., I want a matrix of `92x92`.

such that element (`ci`,`cj`) should be correlation between `ci` and `cj`.

How do I do that?

How can I create a correlation matrix in R?

I write this code to read 3 files, TM is the size of square matrix, LER the No. of rows of an array and from last value define a non-square matrix of (ler/2)*2

Then... the code read a file with some relations, all are numbers and are assign to C[ler].

Then ... C[ler] is assigned to B[ler/2][2].

Those coordinates, per row, in B[ler/2][2] are assign to a and b.

a and b are the row and the column of the matrix A[tm][tm] where to add 1.

My code crashes and I don&#39;t see what the error is.

When I try to compile it, the compiler **gcc -g -o MatSim MatSim.cpp** prompted:

    /usr/include/c++/4.6/iostream:75: undefined reference to `std::ios_base::Init::Init()&#39;
    /usr/include/c++/4.6/iostream:75: undefined reference to `std::ios_base::Init::~Init()&#39;
    collect2: ld returned 1 exit status

Also, when I try to compile it, the compiler **f77 -o MatSim MatSim.cpp** prompted:

    /tmp/cc6ewlkf.o: In function `__static_initialization_and_destruction_0(int, int)&#39;:
    MatSim.cpp:(.text+0x17ad4a): undefined reference to `std::ios_base::Init::Init()&#39;
    MatSim.cpp:(.text+0x17ad4f): undefined reference to `std::ios_base::Init::~Init()&#39;
    collect2: ld returned 1 exit status



**Solution**

The main problem was a library problem, Compile your code using:

     g++ -g -o MatSim MatSim.cpp -lstdc

Still not working?  Install libraries:

    sudo apt-get install g++-multilib





undefined reference to `std::ios_base::Init::Init()&#39;

How to resize image (Bitmap) to for example 800*480 programatically ? I have retrieved a picture in my app which is ~1MB and I need to scale it down to 800*480
I have loaded that picture and compressed it but how do I do to make it smaller :

    ByteArrayOutputStream bos = new ByteArrayOutputStream(8192);
    photo.compress(CompressFormat.JPEG, 25, bos); 

How to resize image (Bitmap) to a given size?

You can understand why I&#39;m trying to find the dominant color in an image if you use Windows 7.  When your mouse over a program in the taskbar, the background of that particular program changes based on the most dominant color in the icon.  I have noticed this technique used in other programs as well, but can&#39;t remember them off the top of my head.

I can see this being helpful in a number of UI techniques that I&#39;m using to develop an application, and I was wondering how finding the most common color would be achieved from an Android drawable resource.

Finding the dominant color of an image in an Android @drawable

I selected console application as my C# project. But the imports that seemed to work under Windows Form project don&#39;t seem to work here. It says that the drawing namespace does not exist.

    using System.Drawing;
    using System.Drawing.Imaging;

My problem is that I need to have the bitmap class. I am trying to make a command line app that does bitmap manipulations to a image. That&#39;s why I didn&#39;t choose my project to be a Windows Form one.

System.drawing namespace not found under console application

I am trying to use the `Notification.Builder.setLargeIcon(bitmap)` that takes a bitmap image. I have the image I want to use in my drawable folder so how do I convert that to bitmap?

converting drawable resource image into bitmap

I am using the following code to rotate a image in ImageView by an angle. Is there any simpler and less complex method available.

    ImageView iv = (ImageView)findViewById(imageviewid);
    TextView tv = (TextView)findViewById(txtViewsid);
    Matrix mat = new Matrix();
    Bitmap bMap = BitmapFactory.decodeResource(getResources(),imageid);
    mat.postRotate(Integer.parseInt(degree));===&gt;angle to be rotated
    Bitmap bMapRotate = Bitmap.createBitmap(bMap, 0, 0,bMap.getWidth(),bMap.getHeight(), mat, true);
    iv.setImageBitmap(bMapRotate);

Android: Rotate image in imageview by an angle

The code for drawing an arrow with *Style: Fill* is given below: 

    paint.setColor(Color.parseColor(&quot;#bdc0dc&quot;));
    paint.setStyle(Style.FILL);
    canvas.drawPath(arrowPath, paint);
    paint.setColor(Color.BLACK);
    paint.setStyle(Style.STROKE);
    paint.setStrokeWidth(2);
    canvas.drawPath(arrowPath, paint);

And the output I obtain is this : 

![enter image description here][1]

Now what I want do is set style to Gradient(Style.gradient not present in android...) to obtain the arrow similar to the image given below : 

![enter image description here][2]

How do i do it ? I tried adding style in style.xml but was unable to add gradient there as it accepts item as parameter..


  [1]: http://i.stack.imgur.com/jc1k2.png
  [2]: http://i.stack.imgur.com/pWXVJ.png

How to set gradient style to paint object?

Can I draw with anti-aliasing on canvas?

I need my circles and line have smooth edges.

Can I draw with antialiasing on canvas?

I&#39;m trying to display a text using the code below.
The problem is that the text is not centered horizontally.
When I set the coordinates for `drawText`, it sets the bottom of the text at this position. I would like the text to be drawn so that the text is centered also horizontally.

This is a picture to display my problem further:

[![Screenshot][1]][2]

    @Override
    protected void onDraw(Canvas canvas) {
		// TODO Auto-generated method stub
		super.onDraw(canvas);
		//canvas.drawRGB(2, 2, 200);
		Paint textPaint = new Paint();
		textPaint.setARGB(200, 254, 0, 0);
		textPaint.setTextAlign(Align.CENTER);
		textPaint.setTypeface(font);
		textPaint.setTextSize(300);
		canvas.drawText(&quot;Hello&quot;, canvas.getWidth()/2, canvas.getHeight()/2  , textPaint);
	}

  [1]: http://i.stack.imgur.com/vEJNbm.png
  [2]: http://i.stack.imgur.com/vEJNb.png

Android Center text on canvas

I have two points in the canvas, now I&#39;m able to draw a line between those points like this below image by using 

This code `canvas.drawLine(p1.x, p1.y, p2.x, p2.y, paint);`
![enter image description here][1]

I want to draw the arc between two points like below image.

![enter image description here][2]

How can I draw like this.


  [1]: http://i.stack.imgur.com/FyMi3.png
  [2]: http://i.stack.imgur.com/he2zj.png

How to draw Arc between two points on the Canvas?

I want to draw text on `canvas` of certain width using `.drawtext`

For example, the width of the text should always be `400px` no matter what the input text is. 

If input text is longer it will decrease the font size, if input text is shorter it will increase the font size accordingly.

Content Type	Original Author	Original Content on Stackoverflow
Question	Yevgeny Simkin	View Question on Stackoverflow
Solution 1 - Android	Albin	View Answer on Stackoverflow

Looking for an explanation of post/pre/set Translate (in Matrix object) and how to use them

Android Problem Overview

Android Solutions

Solution 1 - Android

how to test params passed into a controller in rails 3, using rspec?

Replace substring of NSAttributedString with another NSAttributedString

Attributions