how to get pixel of bitmap image in WP app

Nitin Patil

I'm using namespace System.Windows.Media.Imaging in Windows Phone app and i want to get value of particular pixel value but we can't retrive pixel value because there is no in build method in this namespace like,

img1.getRGB(20, 20);
or
img2.GetPixel(20, 20);
how we can get value of pixel??

4 Replies

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Ramesh Maruthi12y ago
cool thanks Nitin for sharing :)
Nitin Patil12y ago
Image Differences in Windows Phone

we can do many image operation using BItmapImage Class and WritableBitmap Class this two classes. Many image comparison methods are used for archiving high accuracy and for best result. We can use some simple functions of BitmapImage class and WritableBitmap class for archiving image comparison with less coding. For this simple technique we need two WritabaleBitmap images with having same size.

So here some sample code are available for Calculating
Image Differences in WP app.
#wpdev #wp8 #apps #developer

http://wpcsharp.blogspot.in/2014/07/calculate-difference-percentage-of-two-images.html
Nitin Patil12y ago
Thanks Ramesh,
Code is useful for me but i want to calculate percentage of two images after comparison and that images are created by user free hand movements.
e.g.
i have two images img1 and img2 as shown below they are different in shape but has same pattern like 'O'. so i want high matching percentage ratio in this example.

img1 img2
Ramesh Maruthi12y ago
instead of using windows.media can you use this Windows.Graphics.Imaging and try it in this namespace u got a function called GetPixelData()

Otherwise do it in this way

using System;
using System.Diagnostics;
using System.IO;
using System.Linq;
using System.Runtime.InteropServices.WindowsRuntime;
using System.Threading.Tasks;
using Windows.ApplicationModel;
using Windows.UI.Popups;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;
using Windows.UI.Xaml.Media.Imaging;

namespace App110
{
public sealed partial class MainPage : Page
{
public MainPage()
{
this.InitializeComponent();
Test();
}

private async void Test()
{
// Comparing image to itself should return true
Debug.Assert(await ComparePackageImages("Assets\\Logo.png", "Assets\\Logo.png"));

// "Copy of Logo.png" is "Logo.png" with changed one pixel
// and should return false when compared with "Logo.png"
Debug.Assert(!await ComparePackageImages("Assets\\Logo.png", "Assets\\Copy of Logo.png"));

// Two images of different size should
Debug.Assert(!await ComparePackageImages("Assets\\Logo.png", "Assets\\SmallLogo.png"));

await new MessageDialog("Success!").ShowAsync();
Application.Current.Exit();
}

private async Task ComparePackageImages(string packageFilePath1, string packageFilePath2)
{
var b1 = await LoadWriteableBitmapFromPackageFilePath(packageFilePath1);
var b2 = await LoadWriteableBitmapFromPackageFilePath(packageFilePath2);

var pixelStream1 = b1.PixelBuffer.AsStream();
var pixelStream2 = b2.PixelBuffer.AsStream();

return StreamEquals(pixelStream1, pixelStream2);
}

private static async Task LoadWriteableBitmapFromPackageFilePath(string packageFilePath1)
{
var bitmap = new WriteableBitmap(1, 1);
var storageFile = await Package.Current.InstalledLocation.GetFileAsync(packageFilePath1);

using (var streamWithContentType = await storageFile.OpenReadAsync())
{
await bitmap.SetSourceAsync(streamWithContentType);
}

return bitmap;
}

static bool StreamEquals(Stream stream1, Stream stream2)
{
const int bufferSize = 2048;
byte[] buffer1 = new byte[bufferSize]; //buffer size
byte[] buffer2 = new byte[bufferSize];

while (true)
{
int count1 = stream1.Read(buffer1, 0, bufferSize);
int count2 = stream2.Read(buffer2, 0, bufferSize);

if (count1 != count2)
return false;

if (count1 == 0)
return true;

// You might replace the following with an efficient "memcmp"
if (!buffer1.Take(count1).SequenceEqual(buffer2.Take(count2)))
return false;
}
}
}
}