Develop Reference

Display Bitmaps in Xamarin Forms created in Android and iOS

There are the Bitmap for Android and UIImage for iOS. Is there a way to display both somehow in the Xamarin Forms Image control?
Obviously I need the Dependency Service. I will have two implementations that create either a bitmap or an uiimage using some source, but how do I bring those two products together to a single forms control? Both Android and iOS methods have to return something, that the image control can understand and display. I don't know what that might be.
Edit: I look for a way where I don't use storage space, if possible.
Edit2:
I tried Jasons suggestion and it works fine.
I create a bitmap in the Android project and return a MemoryStream object:
MemoryStream stream = new MemoryStream();
newImage.Compress(Bitmap.CompressFormat.Png, 0, stream);
return stream;
Then I consume it in my Xamarin.Forms Image control:
var stream = DependencyService.Get<ICrossPlatformImageProcesor>().Combine_Images(imagePath);
stream.Position = 0;
img_ImageView.Source = Xamarin.Forms.ImageSource.FromStream(() => stream);

I will have two implementations that create either a bitmap or an uiimage using some source, but how do I bring those two products together to a single forms control?
You can simply use Image Control of xamarin forms, images can be loaded specifically for each platform, or they can be downloaded for display.
For more information, you can refer to Working with Images.
I look for a way where I don't use storage space, if possible.
I'm not quite understand this, if you mean don't use memory, then I think it is not possible. If you mean your images are not saved in storage, then possibly you have an URL address on internet of your images?
Anyway, Image control in Xamarin.Forms support image source form ImageSource instance, file, Uri, and resources, to load image from uri, you can simply code like this:
var webImage = new Image { Aspect = Aspect.AspectFit };
webImage.Source = ImageSource.FromUri(new Uri("https://xamarin.com/content/images/pages/forms/example-app.png"));

How to integrate a interactive pdf viewer with in the android application

I am unable to read PDF file from assets folder. how could i read a PDF in a single page with integrating all controls available for a PDF viewer. I don't want to open a default pdf viewer available in the phone. Please suggest me the right way to achieve interactive PDF viewer with in the android application which can read the pdf from assets/raw folder from the android resource components. Thanks in advance

You can use Intent to load your PDF in external application.
File file = //Load your file from assets here
Intent intent = new Intent(Intent.ACTION_VIEW);
intent.setDataAndType(Uri.fromFile(file), "application/pdf");
intent.setFlags(Intent.FLAG_ACTIVITY_NO_HISTORY);
startActivity(intent);
You can load file from assets using InputStream. See this post.
Good luck!

It helped for me:
Barteksc Android Pdf SDK Library
Android PdfViewer AndroidPdfViewer 1.x is available on the
AndroidPdfViewerV1 repo, where can be developed independently. Version
1.x uses a different engine for drawing documents on canvas, so if you don't like the 2.x version, try 1.x.
Library for displaying PDF documents on Android, with animations,
gestures, zoom, and double-tap support. It is based on PdfiumAndroid
for decoding PDF files. Works on API 11 (Android 3.0) and higher.
Licensed under Apache License 2.0.
Which supports Android devices from Android 4.4.4 (KitKat)
Installation
Add to build.gradle:
implementation 'com.github.barteksc:android-pdf-viewer:3.2.0-beta.1'
or if you want to use more stable version:
implementation 'com.github.barteksc:android-pdf-viewer:2.8.2'
Add this into your layout file:
<com.github.barteksc.pdfviewer.PDFView
android:id="#+id/your_pdf_id"
android:layout_width="match_parent"
android:layout_height="match_parent"/>
You can Load a PDF file like this:
pdfView.fromUri(Uri)
or
pdfView.fromFile(File)
or
pdfView.fromBytes(byte[])
or
pdfView.fromStream(InputStream) // stream is written to bytearray - native code cannot use Java Streams
or
pdfView.fromSource(DocumentSource)
or
pdfView.fromAsset(String)
.pages(0, 2, 1, 3, 3, 3) // all pages are displayed by default
.enableSwipe(true) // allows to block changing pages using swipe
.swipeHorizontal(false)
.enableDoubletap(true)
.defaultPage(0)
// allows to draw something on the current page, usually visible in the middle of the screen
.onDraw(onDrawListener)
// allows to draw something on all pages, separately for every page. Called only for visible pages
.onDrawAll(onDrawListener)
.onLoad(onLoadCompleteListener) // called after document is loaded and starts to be rendered
.onPageChange(onPageChangeListener)
.onPageScroll(onPageScrollListener)
.onError(onErrorListener)
.onPageError(onPageErrorListener)
.onRender(onRenderListener) // called after document is rendered for the first time
// called on single tap, return true if handled, false to toggle scroll handle visibility
.onTap(onTapListener)
.onLongPress(onLongPressListener)
.enableAnnotationRendering(false) // render annotations (such as comments, colors or forms)
.password(null)
.scrollHandle(null)
.enableAntialiasing(true) // improve rendering a little bit on low-res screens
// spacing between pages in dp. To define spacing color, set view background
.spacing(0)
.autoSpacing(false) // add dynamic spacing to fit each page on its own on the screen
.linkHandler(DefaultLinkHandler)
.pageFitPolicy(FitPolicy.WIDTH) // mode to fit pages in the view
.fitEachPage(false) // fit each page to the view, else smaller pages are scaled relative to largest page.
.pageSnap(false) // snap pages to screen boundaries
.pageFling(false) // make a fling change only a single page like ViewPager
.nightMode(false) // toggle night mode
.load();
For More Information Github: Barteksc Android Pdf Viewer
I Hope, it Helps!

How do i normalize image in android?

I am working on camera based application.
I want to normalize image that is captured by device's camera.
Is it possible to normalize image in android? any idea how can i do that?
Thanks...

Try to use Catalano Framework. Here contains the article that you can learn how to use.
I implemented Image Normalization using this approach.
FastBitmap fb = new FastBitmap("image.jpg");
fb.toGrayscale();
ImageNormalization in = new ImageNormalization();
in.applyInPlace(fb);

display huge Images in Android

I'm intending to display very large Images in Android. My first solution - to supply them as pdf - fails because not every handheld got a pdf-viewer preinstalled, and I don't want to require the users to install one.
So I have a png now (width = 3998px height=2827px) that I want to display. I downloaded this image to test how it would be displayed the gallery. It was quite painful. It seems that the galery renders this picture only once, and if I Zoom in, I cannot read the text at all.
So I wrote a testActivity which simply has an ImageView nested in a LinearLayout. I put the image into the drawable and set it as ImageView's image-source.
Unforunately the app crashes immediatly, due to an "
ERROR/AndroidRuntime(8906): Caused by: java.lang.OutOfMemoryError: bitmap size exceeds VM budget"
I didn't expect that ONE single Image can be too large forVM's memory. I played a little bit around, set ImageViews size to 3998 & 2827px , put the Image to sdCard and read it manually with a fileInputStream.
To my big surprise it now shows my image, but if I turn my Nexus S horizontal I get the same OutOfMemoryError as before.
Can somewone point me the main difference between recieving a Bitmap through a FileInputStream or to set it as ImageView's source.
Also I'm not able to scroll comfortable with two parent scrollViews
I searching for a simple solution to display ONE large image at a time with the ability to scroll horizontal and vertical while able to zoom in and out.
here is a sample of the image I want to display

I know it's an old post but I spent a lot of time on this problem, so here's my solution.
I wanted to display a 2000×3000 picture but I got out of memory or the image was too large to be displayed.
To begin, I get the dimensions of the picture:
o = new BitmapFactory.Options();
o.inJustDecodeBounds=true;
pictures = BitmapFactory.decodeStream(new FileInputStream(f), null, o);
Then I cut it up into four parts and displayed them with four ImageViews.
I tried to load the full picture and cut it into four (using BitmapFactory.create(bitmap,int,int,int,int)) but got out of memory again.
So I decided to use some BitMapRegionDecoder:
for (int i = 0; i < 2; i++) {
for (int j = 0; j < 2; j++) {
ImageView iv = new ImageView(this);
InputStream istream = null;
try {
istream = this.getContentResolver().openInputStream(Uri.fromFile(f));
} catch (FileNotFoundException e1) {
e1.printStackTrace();
}
BitmapRegionDecoder decoder = null;
try {
decoder = BitmapRegionDecoder.newInstance(istream, false);
} catch (IOException e) {
e.printStackTrace();
}
int nw = (j*width/k);
int nh = (i*height/k);
Bitmap bMap = decoder.decodeRegion(new Rect(nw,nh, (nw+width/k),(nh+height/k)), null);
iv.setImageBitmap(bMap);
}
}
This worked.

I know its an old question but I used TileView to do exactly this:
https://github.com/moagrius/TileView

Try to use this one:
https://github.com/davemorrissey/subsampling-scale-image-view
A custom image view for Android, designed for photo galleries and
displaying huge images (e.g. maps and building plans) without
OutOfMemoryErrors. Includes pinch to zoom, panning, rotation and
animation support, and allows easy extension so you can add your own
overlays and touch event detection.

You can use this "easy to integerate" source of WorldMap application:
https://github.com/johnnylambada/WorldMap
This uses a huge image of a world map, and uses cache to display a map.
To integerate, I just copied all the java files (5 i guess) and used the surfaceView in my layout file. Then I went through the small OnCreate() method of ImageViewerActivity.java and used the code in my activity (with sligh alteration, depending on my personal use).

This post is a good demo for zooming a picture using multi touch gestures. It uses Matrix to zoom as well as pan a picture.

To handle scaling etc and using full resolution, You can use MapView of OSM (open street map) and provide it with your tiles (instead of the map). Check this: http://www.haakseth.com/?p=30

We have to follow following steps to remove out of memory exception while loading huge images:
1. Read Bitmap Dimensions and Type
2. Load a Scaled down version into memory
Android Developer's Guide defines how we achieve these.
here is the link
http://developer.android.com/training/displaying-bitmaps/load-bitmap.html#load-bitmap

Android Photo Viewer Demo

I've been trying to figure out how to display a photo on Android. I can create an ImageView and display a picture, but the functionality is limited (no zoom, pan or share). Is there a demo or tutorial with code out there on how to do this? I've been searching all week with no luck.
Thanks.
P.S.> Please No Snark!
Maybe I don't understand how to create a uri correctly or how to make my resource available to the viewer. I have a resource ID, R.drawable.opal, I'm using to display different minerals and gems for a science project. If the student clicks the small sample photo, then I want to bring up a bigger and better viewer for the photo to allow them to compare to their collected rock.

Unless you really need to build your own you should probably just use the gallery's viewer. Send it the picture by using the view intent like so:
Intent viewImageIntent = new Intent(android.content.Intent.ACTION_VIEW, uri);
startActivity(viewImageIntent);
Replace "uri" with the image's uri of course. Writing your own viewer is really involved and would include threading, physics calculations and handling touch inputs.