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"));
Related
I want to show the app icon from a packageName different than the current one in my flutter app. The platform-channels can't transport drawable / bitmaps. What will be the bast practice for such a task? (It's an Android only feature)
Use
Bitmap.compress (Bitmap.CompressFormat format,
int quality,
OutputStream stream)
to a ByteArrayOutputStream to obtain a byte array in PNG format, which can cross platform-channels, then at the Flutter end turn the resulting List<int> back. (Check whether the List<int> is already a Uint8List, otherwise convert it.)
There are two types of Image in flutter depending on your use case. The normal one is a Widget - create it with Image.memory. The other form (ui.Image) is akin to a bitmap, if you want to draw the resulting image on a Canvas.
Future<Codec> instantiateImageCodec (
Uint8List list
)
I want to upload an internal png image to my backend, the API supplied with the backend only allows for byte[] data to be uploaded.
But so far, I haven't found a way of extracting byte[] data from a texture. If it's an internal resource or not, I'm not sure matters?
So what ways are there to achieve this using Libgdx framework?
The image I want to use is loaded with the AssetManager.
Before trying to do this, make sure to understand the following:
A Texture is an OpenGL resource which resides in video memory (VRAM). The texture data itself is not (necessarily) available in RAM. So you can not access it directly. Transferring that data from VRAM to RAM is comparable to taking a screenshot. In general it is something you want to avoid.
However, if you load the image using AssetManager then you are loading it from file and thus have the data available in RAM already. In that case it is not called a Texture but a Pixmap instead. To get the data from the pixmap goes like this:
Pixmap pixmap = new Pixmap(Gdx.files.internal(filename));
ByteBuffer nativeData = pixmap.getPixels();
byte[] managedData = new byte[nativeData.remaining()];
nativeData.get(managedData);
pixmap.dispose();
Note that you can load the Pixmap using AssetManager as well (in that case you would unload instead of dispose it). The nativeData contains the raw memory, most API's can use that also, so check if you can use that directly. Otherwise you can use the managedData managed byte array.
I want to generate a PDF File from a View using the PdfDocument android class introduced in KitKat. I managed to do it, and the file is so far generated ok, ending up having a correct PDF. The only problem is the file is huge, 12Mb for just one page. Is there a way to reduce the File size?
The code I am using to generate the PDF is:
public static File generateDocument(Activity activity, String fileName, ViewGroup container) throws IOException{
File f = new File(activity.getExternalFilesDir(null), fileName);
PdfDocument document = new PdfDocument();
try{
for(int i=0;i<container.getChildCount();i++){
View v = container.getChildAt(i);
PdfDocument.PageInfo.Builder pageBuilder = new PdfDocument.PageInfo.Builder(v.getWidth(), v.getHeight(), i);
Page page = document.startPage(pageBuilder.create());
v.draw(page.getCanvas());
document.finishPage(page);
}
document.writeTo(new FileOutputStream(f));
} finally{
if(document!=null){
document.close();
}
}
return f;
}
In case anyone is still looking for a solution... I was working on a project to generate PDF from images and not satisfied with the file size generated by both Android's PdfDocument and 3rd party AndroidPdfWriter APW.
After some trials I ended up using Apache's PdfBox, which gave me a PDF file (A4 size with a single 1960x1080 image) for around 80K, while it's usually 2~3M with PdfDocument or AndroidPdfWriter.
PDDocument document = new PDDocument();
PDPage page = new PDPage(PDRectangle.A4);
document.addPage(page);
// Define a content stream for adding to the PDF
contentStream = new PDPageContentStream(document, page);
Bitmap bimap = _get_your_bitmap_();
// Here you have great control of the compression rate and DPI on your image.
// Update 2017/11/22: The DPI param actually is useless as of current version v1.8.9.1 if you take a look into the source code. Compression rate is enough to achieve a much smaller file size.
PDImageXObject ximage = JPEGFactory.createFromImage(document, bitmap, 0.75, 72);
// You may want to call PDPage.getCropBox() in order to place your image
// somewhere inside this page rect with (x, y) and (width, height).
contentStream.drawImage(ximage, 0, 0);
// Make sure that the content stream is closed:
contentStream.close();
document.save(_your_file_path_);
document.close();
=====
btw. I guess the reason why they generate a huge file size is because they don't compress the image data while writing to PDF file. If you take a look into AndroidPdfWriter's XObjectImage.deflateImageData() method you will see it's using java.util.zip.Deflater.NO_COMPRESSION option to write the image data which is kind of horrible if you've got a picture with size 1960x1080. If you change the options to e.g. Deflater.BEST_COMPRESSION you get much smaller file size however it takes up to 3-4 seconds for me to handle one single page which is not acceptable.
There are a few main things that increases the size of a PDF file:
hi-resolution pictures (where lo-res would suffice)
embedded fonts (where content would still be readable "good enough" without them)
PDF content not required any more for the current version/view (older version of certain objects)
embedded ICC profiles
embedded third-party files (using the PDF as a container)
embedded job tickets (for printing)
embedded Javascript
and a few more
Try using iText. Following links give a basice idea for iText in android.
http://technotransit.wordpress.com/2011/06/17/using-itext-in-android/
http://www.mysamplecode.com/2013/05/android-itext-pdf-bluetooth-printer.html
https://stackoverflow.com/a/21025162/3110609
Using PDFDocument, be sure to downscale your images prior to drawing them in the canvas.
When drawing to the screen, this is enough to scale the bitmap :
canvas.drawBitmap(bmp, src, dst, paint);
However, when using the canvas from PdfDocument.Page.getCanvas, this canvas will not downscale the bitmap, it will just squeeze it into a smaller zone. Instead you should do something like this:
// Scale bitmap : filter = false since we are always downSampling
Bitmap scaledBitmap = Bitmap.createScaledBitmap(bmp, dstWidth, dstHeight,
false); // filter=false if downscaling, true if upscaling
canvas.drawBitmap(scaledBitmap, null, dst, paint);
scaledBitmap.recycle();
This is embedded in Android so it is much easier than using a third-party library. (The above was tested on a Marshmallow platform)
This seems to just be a bug in PdfDocument. The PDF file I created with PdfDocument was 5.6 megabytes. The same document generated through the iOS equivalent was 500K. If I take the Android PDF and run it through Adobe Acrobat's pdf optimization, without compressing any images, the 5.6MB file becomes 350K. They look identical, and I applied no compression in Adobe Acrobat.
In the actual PDF code, the Android image object dictionary is this
<</Type /XObject
/Subtype /Image
/Width 1224
/Height 1584
/ColorSpace /DeviceRGB
/BitsPerComponent 8
/Length 5816448
>>
The PDF from iOS has this dict
<< /Length 8 0 R
/Type /XObject
/Subtype /Image
/Width 1224
/Height 1584
/ColorSpace /DeviceRGB
/SMask 9 0 R
/BitsPerComponent 8
/Filter /FlateDecode >>
I think the problem is the lack of the FlateDecode filter in the Android version. When I run it through the Adobe Acrobat PDF optimizer, it gets the FlateDecode filter.
orI have an app that is consistently downloading large images from a parse back-end. In android you can download the images as streams using their URI's and set a specific dimension size to the bitmap that I want to download. Usually this is done using the BitmapFactory libraries and allows me to download a bitmap that's of a scaled down size, saving my app from long loading times. Is there an equivalency to this method on the IOS platform? This is what I am currently doing, but when I download 15 full sized images I get a large amount of load time:
//where photoQuery is a Parse.com database query that returns the photo as the first object
PFObject *photoObject = [photoQuery getFirstObject];
PFFile *photoFile = (PFFile *)[photoObject objectForKey:#"fullSizedImage"];
UIImage *fullImage = [UIImage imageWithData:photoFile.getData];
Does IOS support something similar to BitmapFactory or this common android design pattern?
PFFile has a method called – getDataInBackgroundWithBlock:. Which can be used like this:
[photoFile getDataInBackgroundWithBlock:^(NSData *data, NSError *error) {
if(!error) {
[imageView setImage:[UIImage imageWithData:data];
}
}
Or you can use another method called - getDataStreamInBackgroundWithBlock:. It is similar as the one above. The difference is the first parameter of the block is a NSInputStream
PFImageView should help you load these images a synchronously. You may try thumbnailing images using Cloud Code.
Is there any way to get a high resolution screen shot of a certain view in an activity.
I want to convert html content of my webview to PDF. For that I tried to take screen shot of the webview content and then converted it to PDF using itext. The resulted PDF is not in much more clarity.
My code:
protected void takeimg() {
Picture picture = mWebView.capturePicture();
Bitmap b = Bitmap.createBitmap(picture.getWidth(), picture.getHeight(),
Bitmap.Config.ARGB_8888);
Canvas c = new Canvas(b);
picture.draw(c);
// byte[] bt = b.getNinePatchChunk();
// Bitmap b;
// View v1 = mWebView.getRootView();
// v1.setDrawingCacheEnabled(true);
// b = Bitmap.createBitmap(v1.getDrawingCache());
// v1.setDrawingCacheEnabled(false);
FileOutputStream fos = null;
try {
File root = new File(Environment.getExternalStorageDirectory(),
"Sample");
if (!root.exists()) {
root.mkdir();
}
String sdcardhtmlpath = root.getPath().toString() + "/"
+ "temp_1.png";
fos = new FileOutputStream(sdcardhtmlpath);
// fos = openFileOutput("samsp_1.jpg", MODE_WORLD_WRITEABLE);
if (fos != null) {
b.compress(Bitmap.CompressFormat.PNG, 100, fos);
// fos.write(bt);
fos.close();
}
} catch (Exception e) {
Log.e("takeimg", e.toString());
e.printStackTrace();
}
}
protected void pdfimg() {
Document mydoc = new Document(PageSize.A3);
try {
File root = new File(Environment.getExternalStorageDirectory(),
"Sample");
if (!root.exists()) {
root.mkdir();
}
String sdcardhtmlpath = root.getPath().toString() + "/";
mydoc.setMargins(0, 0, 0, 0);
PdfWriter.getInstance(mydoc, new FileOutputStream(sdcardhtmlpath
+ PDFfilename));
mydoc.open();
Image image1 = Image.getInstance(sdcardhtmlpath + "temp_1.jpg");
image1.scalePercent(95f);
mydoc.add(image1);
// mydoc.newPage();
mydoc.close();
} catch (Exception e) {
Log.e("pdi name", e.toString());
}
}
Update: See Edit 3 for an answer to op's original question
There are two options:
Use a library to convert the HTML to PDF. This is by far the best option, since it will (probably) preserve text as vectors.
Get a high resolution render of the HTML and save it as a PNG (not PDF surely!).
For HTML to PDF, wkhtmltopdf looks like a good option, but it relies on Qt which you can't really use on Android. There are some other libraries but I doubt they do the PDF rendering very well.
For getting a high-res webview, you could try creating your own WebView and calling onMeasure(...) and onLayout(...) and pass appropriate parameters so the view is really big. Then call onDraw(myOwnCanvas) and the webview will draw itself to your canvas, which can be backed by a Bitmap using Canvas.setBitmap().
You can probably copy the state into the new WebView using something like
screenshotterWebview.onRestoreInstanceState(mWebView.onSaveInstanceState());
Orrr it may even be possible to use the same WebView, just temporarily resize it to be large, onDraw() it to your canvas, and resize it back again. That's getting very hacky though!
You might run into memory issues if you make it too big.
Edit 1
I thought of a third, exactly-what-you-want option, but it's kind of hardcore. You can create a custom Canvas, that writes to a PDF. In fact, it is almost easy, because underlying Canvas is Skia, which actually includes a PDF backend. Unfortunately you don't get access to it on Android, so you'll basically have to build your own copy of it on Android (there are instructions), and duplicate/override all the Canvas methods to point to your Skia instead of Androids. Note that there is a tempting Picture.writeToStream() method which serializes the Skia data, but unfortunately this format is not forwards or backwards compatible so if you use it your code will probably only work on a few versions of Android.
I'll update if/when I have fully working code.
Edit 2
Actually it is impossible to make your own "intercepting" Canvas. I started doing it and went through the tedious process of serializing all function calls. A few you can't do because they are hidden, but those didn't look important. But right at the end I came to serializing Path only to discover that it is write-only. That seems like a killer to me, so the only option is to interpret the result of Picture.writeToStream(). Fortunately there are only two versions of that format in use, and they are nearly identical.
Edit 3 - Really simple way to get a high resolution Bitmap of a view
Ok, it turns out just getting a high res bitmap of a view (which can be the entire app) is trivial. Here is how to get double resolution. Obviously all the bitmaps look a bit crap, but the text is rendered at full resolution:
View window = activity.getWindow().getDecorView()
Canvas bitmapCanvas = new Canvas();
Bitmap bitmap = Bitmap.createBitmap(window.getWidth()*2, window.getHeight()*2, Bitmap.Config.ARGB_8888);
bitmapCanvas.setBitmap(bitmap);
bitmapCanvas.scale(2.0f, 2.0f);
window.draw(bitmapCanvas);
bitmap.compress(Bitmap.CompressFormat.PNG, 0, myOutputStream);
Works like a charm. I've now given up on getting a PDF screenshot with vector text. It's certainly possible, but very difficult. Instead I am working on getting a high-res PSD where each draw operation is a separate layer, which should be much easier.
Edit 4
Woa this is getting a bit long, but success! I've generated an .xcf (GIMP) and PDF where each layer is a different canvas drawing operation. It's not quite as fine-grained as I was expecting, but still, pretty useful!
Actually my code just outputs full-size PNGs and I used "Open as layers..." and "Autocrop layer" in GIMP to make these files, but of course you can do that in code if you like. I think I will turn this into a blog post.
Download the GIMP or Photoshop demo file (rendered at 3x resolution).
When you capture the view, just screen bound will capture ( due to control weight and android render pipeline ).
Capturing screenshot for converting to PDF is tricky way. I think two way is more reasonable solutions.
Solution #1
Write a parser ( it's simple ) to convert webview content ( that is HTML ) to iText format.
You can refer to this article for more information.
http://www.vogella.com/articles/JavaPDF/article.html
Also to write a parser you can use REGEX and provide your own methods like parseTable, parseImage, ...
Solution #2 Internet Required
Provide a URL ( or webservice ) to convert HTML to PDF using PHP or C# that has a lot of nice libraries. Next you can send download link to the Client ( Android Device ).
So you can also dynamically add some Tags, Banners, ... to the PDF from server side.
Screen Shot is nothing but picture of your device display which usually depend upon your phone absolute pixels, if your phone is 480x800 screen shot will be same and generally applicable for all scenarios.
Sure, Use this:
Bitmap bitmap;
View v1 = MyView.getRootView();
v1.setDrawingCacheEnabled(true);
bitmap = Bitmap.createBitmap(v1.getDrawingCache());
v1.setDrawingCacheEnabled(false);
Here MyView is the View you need a screenshot of.