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Android and setting width and height programmatically in dp units

I'm doing:

button.setLayoutParams(new GridView.LayoutParams(65, 65));

According to the docs the units for the width and height (both 65 in the above) are "pixels". How do you force this to be device independent pixels, or "dp"?

What does the filter parameter to createScaledBitmap do?

The declaration of android.graphics.Bitmap.createScaledBitmap is

public static Bitmap createScaledBitmap
  (Bitmap src, int dstWidth, int dstHeight, boolean filter)

However, the documentation doesn't explain any of the parameters. All of them are pretty obvious except for boolean filter. Does anyone know what it does?

How to scale down a range of numbers with a known min and max value

So I am trying to figure out how to take a range of numbers and scale the values down to fit a range. The reason for wanting to do this is that I am trying to draw ellipses in a java swing jpanel. I want the height and width of each ellipse to be in a range of say 1-30. I have methods that find the minimum and maximum values from my data set, but I won't have the min and max until runtime. Is there an easy way to do this?

How do I scale one rectangle to the maximum size possible within another rectangle?

I have a source rectangle and a destination rectangle. I need to find the maximum scale to which the source can be scaled while fitting within the destination rectangle and maintaining its original aspect ratio.

Google found one way to do it but I'm not sure if it works in all cases. Here is my home-brewed solution:

• Calculate Height/Width for each rectangle. This gives the slopes of the diagonals msrc and mdest.
• If msrc < mdst, scale source width to fit the destination width (and scale height by the same ratio)
• Otherwise, scale source height to fit the destination height (and scale width by the same ratio)

Looking for other possible solutions to this problem. I'm not even sure if my algorithm works in all cases!

How to scale MySQL with multiple machines?

I have a web app running LAMP. We recently have an increase in load and is now looking at solutions to scale. Scaling apache is pretty easy we are just going to have multiple multiple machines hosting it and round robin the incoming traffic.

However, each instance of apache will talk with MySQL and eventually MySQL will be overloaded. How to scale MySQL across multiple machines in this setup? I have already looked at this but specifically we need the updates from the DB available immediately so I don't think replication is a good strategy here? Also hopefully this can be done with minimal code change.

PS. We have around a 1:1 read-write ratio.

Scaled Bitmap maintaining aspect ratio

I would like to scale a Bitmap to a runtime dependant width and height, where the aspect ratio is maintained and the Bitmap fills the entire width and centers the image vertically, either cropping the excess or filling in the gap with 0 alpha pixels.

I'm currently redrawing the bitmap myself by creating a Bitmap of all 0 alpha pixels and drawing the image Bitmap on top of it, scaling to the exact specified width and maintaining the aspect ratio, however, it ends up losing/screwing up the pixel data.

Here is how I'm doing it:

Bitmap background = Bitmap.createBitmap((int)width, (int)height, Config.ARGB_8888);
float originalWidth = originalImage.getWidth(), originalHeight = originalImage.getHeight();
Canvas canvas = new Canvas(background);
float scale = width/originalWidth;
float xTranslation = 0.0f, yTranslation = (height - originalHeight * scale)/2.0f;
Matrix transformation = new Matrix();
transformation.postTranslate(xTranslation, yTranslation);
transformation.preScale(scale, scale);
canvas.drawBitmap(originalImage, transformation, null);
return background;

Is there a library out there or some better code that can do this better? I would like the image to look as crisp as possible, but I knew that my function wouldn't provide a great result.

I know I could have the image stay fine by using integer scaling, instead of float scaling, but I need the width to be 100% filled.

Also, I know about an ImageView's Gravity.CENTER_CROP capability, however, that also uses integer scaling, so it cuts off the width of the image when it shouldn't.

CSS scale down image to fit in containing div, without specifing original size

I want to have a website where I can upload images of different sizes to be displayed in a jquery slider. I can't seem to fit (scaling down) the image in a containing div. Here's how I'm intending to do it

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org    /TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Untitled Document</title> 
<link rel="stylesheet" type="text/css" rel='nofollow' href="Imtest.css"/>
</head>

<body>

<div id="wrapper"> 

<div id="im"><img src="Images/Scarpa2_1.jpg" /></div>

</div>  
</body>
</html>

And the CSS

#wrapper {
    width: 400px;
    height: 400px;
    border: 2px black solid;
    margin: auto;
}

#im {
    max-width: 100%;
}

I've tried to set the max-width of my image to 100% in CSS. But that doens't work.

Service Oriented Architecture - AMQP or HTTP

A little background.

Very big monolithic Django application. All components use the same database. We need to separate services so we can independently upgrade some parts of the system without affecting the rest.

We use RabbitMQ as a broker to Celery.

Right now we have two options:

1. HTTP Services using a REST interface.
2. JSONRPC over AMQP to a event loop service

My team is leaning towards HTTP because that's what they are familiar with but I think the advantages of using RPC over AMQP far outweigh it.

AMQP provides us with the capabilities to easily add in load balancing, and high availability, with guaranteed message deliveries.

Whereas with HTTP we have to create client HTTP wrappers to work with the REST interfaces, we have to put in a load balancer and set up that infrastructure in order to have HA etc.

With AMQP I can just spawn another instance of the service, it will connect to the same queue as the other instances and bam, HA and load balancing.

Am I missing something with my thoughts on AMQP?

Gems/Services for autoscaling Heroku's dynos and workers

I want to know if there are any good solutions for autoscaling dynos AND workers on Heroku in a production environment (probably a different solution for each of those, as they are pretty unrelated). What are you/companies using, regarding this?

I found lots of options, but none of them seem really mature for a production environment. There is Heroscale, which seem to introduce some latency as it does not run locally, and I also heard of some downtime. There are modifications of delayed_jobs, which have not been updated for a long time, and there are some issues with current bundlers. There is also some alternatives related to reque, which seem not to handle very well some HTTP exceptions, which results in app crashing, and others which seem to need an always-running worker to schedule other workers, and may also suffer from some HTTP exceptions problems.

Well. In the end. What is being used, nowadays, for autoscaling Heroku's dynos and workers on a production environment with Rails3?

Thanks in advance.

Trying to multiply a number from 0..4096 by 0.3 using only integer math

I'm trying to wrap my head around how I'd multiply a number from 0..4096 by 0.3 using just integers with shift operations and scaling, without dividing, in C. I'm new to this stuff and any input or step by step suggestions would be extremely helpful.

How to disable web page zooming/scaling on Android?

I have written a small web app to collect some data and store it in a central database. I'm walking around, reading values and typing them into a web site on my Android smartphone. It's just for me, so no public usability concerns apply this time.

Now I want to add a button to increment a reading by one, and I need to be able to push that button several times. But if I do it too fast, the browser recognises a double-tab and scales/zooms into the page.

I have added a viewport header already and played with every value combination I could find on the web. But the page remains scalable. How can I stop that?

Here's a minimal test page that fails for me:

<!doctype html>
<html>
<head>
<title>Test page</title>
<meta name="viewport" content="width=device-width, user-scalable=no" />
<style type="text/css">
body
{
    font: 16pt sans-serif;
}
</style>
</head>
<body>
This is a test page. It should not be scalable by the user at all. Not with the two-pinger pinch gesture and even less with a double-tap on the text.
</body>
</html>

Adding initial-scale=1, maximum-scale=1 and all sorts of target-whateveritwas-dpi doesn't change a thing. I have restarted the browser (Dolphin HD and the stock browser) and cleared the cache already. I'm on Android 2.2, the phone is an HTC Desire.

Strange HTML5 Canvas drawImage behaviour

I am writing some code that uses HTML5 canvas. Generally it works well, but now I found a very strange behaviour. The weird thing is that it is consistent on different browsers, so must be that I understood the thing wrong... Despite the docs seem to say exactly what I am doing. Here is the code (it's an object method):

   MyCanvas.prototype.getElement = function() {

        var innerHtml = "<div></div>";

        var elem = jQuery(innerHtml, {
            'id' : this.viewId
        });



        var canvas = jQuery("<canvas/>", {
            'id' : this.viewId + "canvas",
            'width' : this.width,
            'height' : this.height
        });

        var w = this.width;
        var h = this.height;

        jQuery(elem).append(canvas);

        var imgElem = new Image();

        imgElem.src = this.maskImage;
        imgElem.onload = function() {
            var ctx = canvas[0].getContext('2d');
            ctx.drawImage(this, 0, 0, w, h);

        };

        return elem;
    };

After this I'll use jQuery again to append this element to a Div that is already in the page (which is blank). The result will be that the image is overstretched like ten times it's width.... That is weird because, for what I understood of drawImage, it should use the w and h values to scale the image and given that w and h are the size of the canvas, it should fit well.

What am I doing wrong? Is it because I do the drawing off the rendered DOM tree?

Android: high quality image resizing / scaling

I need to scale down images coming from a Network stream without losing quality.

I am aware of this solution Android: Strange out of memory issue but it is too coarse - inSampleSize is an integer and does not allow finer control over the resulting dimensions. That is, I need to scale images to specific h/w dimensions (and keeping aspect ratio).

I dont mind having a DIY bicubic/lancoz algorithm in my code but I cant find any examples that would work on Android as they all rely on Java2D (JavaSE).

EDIT: Ive attached a quick source. The original is 720x402 HD screen capture. Please ignore the top 2 thumbnails. The top large image is resized automatically by android (as part of layout) to about 130x72. It is nice and crisp. The bottom image is resized with API and has severe artifacting

I've also tried using the BitmapFactory and, as I said earlier, it has two problems - no way to scale to exact size and the scaled image is blurry.

Any ideas on how to fix the artifcating?

Thanks, S.O.!

    package qp.test;

import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Matrix;
import android.os.Bundle;
import android.widget.ImageView;

public class imgview extends Activity {

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        Bitmap original = BitmapFactory.decodeResource(getResources(), R.drawable.a000001570402);
        Bitmap resized = getResizedBitmap(original, 130);
        //Bitmap resized = getResizedBitmap2(original, 0.3f);
        System.err.println(resized.getWidth() + "x" + resized.getHeight());

        ImageView image = (ImageView) findViewById(R.id.ImageViewFullManual);
        image.setImageBitmap(resized);

    }

    private Bitmap getResizedBitmap(Bitmap bm, int newWidth) {

        int width = bm.getWidth();

        int height = bm.getHeight();

    float aspect = (float)width / height;

    float scaleWidth = newWidth;

    float scaleHeight = scaleWidth / aspect;        // yeah!

    // create a matrix for the manipulation

    Matrix matrix = new Matrix();

    // resize the bit map

    matrix.postScale(scaleWidth / width, scaleHeight / height);

    // recreate the new Bitmap

    Bitmap resizedBitmap = Bitmap.createBitmap(bm, 0, 0, width, height, matrix, true);

        bm.recycle();

        return resizedBitmap;
    }

    private Bitmap getResizedBitmap2(Bitmap bm, float scale) {

    /*    float aspect = bm.getWidth() / bm.getHeight();

        int scaleWidth = (int) (bm.getWidth() * scale);
        int scaleHeight = (int) (bm.getHeight() * scale);
*/
        // original image is 720x402 and SampleSize=4 produces 180x102, which is
        // still too large

        BitmapFactory.Options bfo = new BitmapFactory.Options();
        bfo.inSampleSize = 4;

        return BitmapFactory.decodeResource(getResources(), R.drawable.a000001570402, bfo);
    }

}

And the layout

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    >
<!-- <TextView  
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content" 
    android:text="hullo" android:background="#00ff00"
    />
     -->
    <ImageView android:id="@+id/ImageViewThumbAuto"
            android:layout_width="130dip" android:layout_height="72dip"
            android:src="@drawable/a000001570402"  />

    <ImageView android:id="@+id/ImageViewThumbManual"
            android:layout_width="130dip" android:layout_height="72dip"
            android:src="@drawable/a000001570402"  
            android:layout_toRightOf="@id/ImageViewThumbAuto"
            />

<ImageView android:id="@+id/ImageViewFullAuto" android:layout_width="300dip"
            android:layout_height="169dip"
            android:scaleType="fitXY"
            android:src="@drawable/a000001570402"
            android:layout_below="@id/ImageViewThumbAuto"
            />

<ImageView android:id="@+id/ImageViewFullManual" android:layout_width="300dip"
            android:layout_height="169dip"
            android:scaleType="fitXY"
            android:src="@drawable/a000001570402"
            android:layout_below="@id/ImageViewFullAuto"
            />

</RelativeLayout>

Scale image keeping its aspect ratio in background drawable

How do I make a background image fit the view but keep its aspect ratio when using <bitmap /> as a background drawable xml? None of <bitmap>'s android:gravity values gives the desired effect.

Best practice for rate limiting users of a REST API?

I am putting together a REST API and as I'm unsure how it will scale or what the demand for it will be, I'd like to be able to rate limit uses of it as well as to be able to temporarily refuse requests when the box is over capacity or if there is some kind of slashdotted scenario.

I'd also like to be able to gracefully bring the service down temporarily (while giving clients results that indicate the main service is offline for a bit) when/if I need to scale the service by adding more capacity.

Are there any best practices for this kind of thing? Implementation is Rails with mysql.