I'm using muPDF for reading PDFs in my application. I don't like its default animation (Switching horizontally). In other side i found this brilliant library for curl effect on images, and this project for flip-flap effect on layouts.
In curl sample project, in CurlActivity, all of data are images and set in PageProvider like this:
private class PageProvider implements CurlView.PageProvider {
// Bitmap resources.
private int[] mBitmapIds = { R.drawable.image1, R.drawable.image2,
R.drawable.image3, R.drawable.image4};
And use it like this:
private CurlView mCurlView;
mCurlView = (CurlView) findViewById(R.id.curl);
mCurlView.setPageProvider(new PageProvider());
And CurlView extends from GLSurfaceView and implements View.OnTouchListener, CurlRenderer.Observer
But in muPDF if i'm not mistaken, data are in core object. core is instance of MuPDFCore. And using it like this:
MuPDFReaderView mDocView;
MuPDFView pageView = (MuPDFView) mDocView.getDisplayedView();
mDocView.setAdapter(new MuPDFPageAdapter(this, this, core));
MuPDFReaderView extends ReaderView and ReaderView extends AdapterView<Adapter> and implements GestureDetector.OnGestureListener, ScaleGestureDetector.OnScaleGestureListener, Runnable.
My question is where how can I using curl effect in muPDF? Where should I get pages one by one and converting them to bitmaps? and then changing aspects of the Adapter in muPDF to CurlView.
In flip-flap sample project, in FlipHorizontalLayoutActivity (I like this effect too), we have these:
private FlipViewController flipView;
flipView = new FlipViewController(this, FlipViewController.HORIZONTAL);
flipView.setAdapter(new TravelAdapter(this));
setContentView(flipView);
And FlipViewController extends AdapterView<Adapter>, and data set in TravelAdapter that extends BaseAdapter.
No one has done this before? Or can help me to do that?!
EDIT:
I found another good open source PDF reader with curl effect called fbreaderJ. its developer says "An additional module that allows to open PDF files in FBReader. Based on radaee pdf library."
I got confused! cause radaeepdf is closed source and downloadable project is just for demo and inserted username and password is for this package.
People want to change whole fbreader project such as package name.
Another issue for make me confused is where is this additional module source code?!
Anyway, if someone wants to help me, fbreader has done it very well.
EDIT:
I talked to Robin Watts, who developed muPDF (or one of developers), and he said:
Have you read platform/android/ClassStructure.txt ? MuPDF is
primarily a C library. The standard api is therefore a C one. Rather
than exposing that api exactly as is to Java (which would be the
nicest solution, and something that I've done some work on, but have
not completed due to lack of time), we've implemented MuPDFCore to
wrap up just the bits we needed. MuPDFCore handles opening a PDF file,
and getting bitmaps from it to be used in views. or rather, MuPDFCore
returns 'views', not 'bitmaps'. If you need bitmaps, then you're going
to need to make changes in MuPDFCore.
There are too many errors when changing a little part of MuPDFReaderView class. I get confused! These are related to each other.
Please answer more precisely.
EDIT:
And bounty has expired.
If the muPDF does not support rendering to a bitmap, you have no other choice than rendering to a regular view and take a screen dump to a bitmap like this:
View content = findViewById(R.id.yourPdfView);
Bitmap bitmap = content.getDrawingCache();
Then use this bitmap as input to your other library.
Where should i get pages one by one and converting them to bitmaps?
In our application (newspaper app) we use MuPDF to render PDFs.
The workflow goes like this:
Download PDF file (we have one PDF per newspaper page)
Render it with MuPDF
Save the bitmap to the filesystem
Load the Bitmap from filesystem as background image to a view
So, finally, what we use is MuPDFCore.java and its methods drawPage(...) and onDestroy()
Is this what you want to know or do i miss the point?
EDIT
1.) I think it is not necessary to post code how to download a file. But after downloading i add a RenderTask (extends from Runnable) to a Renderqueue and trigger that queue. The RenderTask needs some information for rendering:
/**
* constructs a new RenderTask instance
* #param context: you need Context for MuPdfCore instance
* #param pageNumber
* #param pathToPdf
* #param renderCallback: callback to set bitmap to the view after
* rendering
* #param heightOfRenderedBitmap: this is the target height
* #param widthOfRenderedBitmap: this is the target width
*/
public RenderTask (Context context, Integer pageNumber, String pathToPdf, IRenderCallback,
renderCallback, int heightOfRenderedBitmap,
int widthOfRenderedBitmap) {
//store things in fields
}
2.) + 3.) The Renderqueue wraps the RenderTask in a new Thread and starts it. So the run-method of the RenderTask will be invoked:
#Override
public void run () {
//do not render it if file exists
if (exists () == true) {
finish();
return;
}
Bitmap bitmap = render();
//if something went wrong, we can't store the bitmap
if (bitmap == null) {
finish();
return;
}
//now save the bitmap
// in my case i save the destination path in a String field
imagePath = save(bitmap, new File("path/to/your/destination/folder/" + pageNumber + ".jpg"));
bitmap.recycle();
finish();
}
/**
* let's trigger the callback
*/
private void finish () {
if (renderCallback != null) {
// i send the whole Rendertask to callback
// maybe in your case it is enough to send the pageNumber or path to
// renderend bitmap
renderCallback.finished(this);
}
}
/**
* renders a bitmap
* #return
*/
private Bitmap render() {
MuPDFCore core = null;
try {
core = new MuPDFCore(context, pathToPdf);
} catch (Exception e) {
return null;
}
Bitmap bm = Bitmap.createBitmap(widthOfRenderedBitmap, heightOfRenderedBitmap, Config.ARGB_8888);
// here you render the WHOLE pdf cause patch-x/-y == 0
core.drawPage(bm, 0, widthOfRenderedBitmap, heightOfRenderedBitmap, 0, 0, widthOfRenderedBitmap, heightOfRenderedBitmap, core.new Cookie());
core.onDestroy();
core = null;
return bm;
}
/**
* saves bitmap to filesystem
* #param bitmap
* #param image
* #return
*/
private String save(Bitmap bitmap, File image) {
FileOutputStream out = null;
try {
out = new FileOutputStream(image.getAbsolutePath());
bitmap.compress(Bitmap.CompressFormat.JPEG, 80, out);
return image.getAbsolutePath();
} catch (Exception e) {
return null;
}
finally {
try {
if (out != null) {
out.close();
}
} catch(Throwable ignore) {}
}
}
}
4.) I think it is not necessary to post code how to set a bitmap as background of a view
Related
I am working on an app that uses a Recyclerview to display mp3 files, providing its cover art image along with other info. It works but is slow once it starts dealing with a dozen or more cover arts to retrieve, as I am currently doing this from the id3 on the main thread, which I know is not a good idea.
Ideally, I would work with placeholders so that the images can be added as they become available. I've been looking into moving the retrieval to a background thread and have looked at different options: AsyncTask, Service, WorkManager. AsyncTask seems not to be the way to go as I face memory leaks (I need context to retrieve the cover art through MetadataRetriever). So I am leaning away from that. Yet I am struggling to figure out which approach is best in my case.
From what I understand I need to find an approach that allows multithreading and also a means to cancel the retrieval in case the user has already moved on (scrolling or navigating away). I am already using Glide, which I understand should help with the caching.
I know I could rework the whole approach and provide the cover art as images separately, but that seems a last resort to me, as I would rather not weigh down the app with even more data.
The current version of the app is here (please note it will not run as I cannot openly divulge certain aspects). I am retrieving the cover art as follows (on the main thread):
static public Bitmap getCoverArt(Uri medUri, Context ctxt) {
MediaMetadataRetriever mmr = new MediaMetadataRetriever();
mmr.setDataSource(ctxt, medUri);
byte[] data = mmr.getEmbeddedPicture();
if (data != null) {
return BitmapFactory.decodeByteArray(data, 0, data.length);
} else {
return null;
}
}
I've found many examples with AsyncTask or just keeping the MetaDataRetriever on the main thread, but have yet to find an example that enables a dozen or more cover arts to be retrieved without slowing down the main thread. I would appreciate any help and pointers.
It turns out it does work with AsyncTask, as long as it is not a class onto itself but setup and called from a class with context. Here is a whittled down version of my approach (I am calling this from within my Adapter.):
//set up titles and placeholder image so we needn't wait on the image to load
titleTv.setText(selectedMed.getTitle());
subtitleTv.setText(selectedMed.getSubtitle());
imageIv.setImageResource(R.drawable.ic_launcher_foreground);
imageIv.setAlpha((float) 0.2);
final long[] duration = new long[1];
//a Caching system that helps reduce the amount of loading needed. See: https://github.com/cbonan/BitmapFun?files=1
if (lruCacheManager.getBitmapFromMemCache(selectedMed.getId() + position) != null) {
//is there an earlier cached image to reuse? imageIv.setImageBitmap(lruCacheManager.getBitmapFromMemCache(selectedMed.getId() + position));
imageIv.setAlpha((float) 1.0);
titleTv.setVisibility(View.GONE);
subtitleTv.setVisibility(View.GONE);
} else {
//time to load and show the image. For good measure, the duration is also queried, as this also needs the setDataSource which causes slow down
new AsyncTask<Uri, Void, Bitmap>() {
#Override
protected Bitmap doInBackground(Uri... uris) {
MediaMetadataRetriever mmr = new MediaMetadataRetriever();
mmr.setDataSource(ctxt, medUri);
byte[] data = mmr.getEmbeddedPicture();
Log.v(TAG, "async data: " + Arrays.toString(data));
String durationStr = mmr.extractMetadata(MediaMetadataRetriever.METADATA_KEY_DURATION);
duration[0] = Long.parseLong(durationStr);
if (data != null) {
InputStream is = new ByteArrayInputStream(mmr.getEmbeddedPicture());
return BitmapFactory.decodeStream(is);
} else {
return null;
}
}
#Override
protected void onPostExecute(Bitmap bitmap) {
super.onPostExecute(bitmap);
durationTv.setVisibility(View.VISIBLE);
durationTv.setText(getDisplayTime(duration[0], false));
if (bitmap != null) {
imageIv.setImageBitmap(bitmap);
imageIv.setAlpha((float) 1.0);
titleTv.setVisibility(View.GONE);
subtitleTv.setVisibility(View.GONE);
} else {
titleTv.setVisibility(View.VISIBLE);
subtitleTv.setVisibility(View.VISIBLE);
}
lruCacheManager.addBitmapToMemCache(bitmap, selectedMed.getId() + position);
}
}.execute(medUri);
}
I have tried working with Glide for the caching, but I haven't been able to link the showing/hiding of the TextViews to whether there is a bitmap. In a way though, this is sleeker as I don't need to load the bulk of the Glide-library. So I am happy with this for now.
EDIT: This is a bug in Android version <4.3 Kitkat. It relates to the libjpeg library in Android, which can't handle JPEGs with missing EOF/EOI bits, or apparently with metadata/EXIF data that it doesn't like.
https://code.google.com/p/android/issues/detail?id=9064
ORIGINAL QUESTION:
I have an issue when loading an image in my app.
My endpoint sends JSON which contains a BASE64 encoded image. Depending on the REST call, these images can be PNG or JPG. Some of the JPG files suffer from an issue where they are missing an EOF bit at the end. The PNG files work, and some JPG files work, but unfortunately a lot of these JPG files with the issue are present in the Oracle DB (stored as BLOB). I don't have control of the DB.
I have been looking through Google bugs here:
https://code.google.com/p/android/issues/detail?id=9064
and here:
https://code.google.com/p/android/issues/detail?id=57502
The issue is also seen where the encoding is CYMK using a custom ICC profile.
Decoding the image the standard way returns false:
byte[] imageAsBytes = Base64.decode(base64ImageString, Base64.DEFAULT);
return BitmapFactory.decodeByteArray(imageAsBytes, 0, imageAsBytes.length);
According to the bug reports above, the built in JPG parser in Android is to blame.
I'm trying to figure out a workaround for my device, which is stuck on 4.2.2. I have no other option on this OS version.
I thought it might be a good idea to try and use an image loader library like Universal Image Loader, but it requires I either have the image stored locally, or stored on a URL. As I get the data in BASE64 from the REST server, I can't use this. An option is to support decodeByteArray in a custom class that extends BaseImageDecoder, as stated by the dev at the bottom here: https://github.com/nostra13/Android-Universal-Image-Loader/issues/209
Here's where I get stuck. I already have a custom image decoder to try handle the issue of the missing EOF marker in the JPG file, but I don't know how to edit it to add support for decodeByteArray.
Here is my CustomImageDecoder:
public class CustomImageDecoder extends BaseImageDecoder {
public CustomImageDecoder(boolean loggingEnabled) {
super(loggingEnabled);
}
#Override
protected InputStream getImageStream(ImageDecodingInfo decodingInfo) throws IOException {
InputStream stream = decodingInfo.getDownloader()
.getStream(decodingInfo.getImageUri(), decodingInfo.getExtraForDownloader());
return stream == null ? null : new JpegClosedInputStream(stream);
}
private class JpegClosedInputStream extends InputStream {
private static final int JPEG_EOI_1 = 0xFF;
private static final int JPEG_EOI_2 = 0xD9;
private final InputStream inputStream;
private int bytesPastEnd;
private JpegClosedInputStream(final InputStream iInputStream) {
inputStream = iInputStream;
bytesPastEnd = 0;
}
#Override
public int read() throws IOException {
int buffer = inputStream.read();
if (buffer == -1) {
if (bytesPastEnd > 0) {
buffer = JPEG_EOI_2;
} else {
++bytesPastEnd;
buffer = JPEG_EOI_1;
}
}
return buffer;
}
}
}
By the way, using the above custom class, I am trying to load my byte array like this:
byte[] bytes = Base64.decode(formattedB64String, Base64.NO_WRAP);
ByteArrayInputStream is = new ByteArrayInputStream(bytes);
String imageId = "stream://" + is.hashCode();
...
ImageLoader imageLoader = ImageLoader.getInstance();
imageLoader.displayImage(imageId, userImage, options);
and I get this error:
ImageLoader: Image can't be decoded [stream://1097215584_656x383]
Universal Image loader does not allow the stream:// schema, so I created a custom BaseImageDownloader class that allows it:
public class StreamImageDownloader extends BaseImageDownloader {
private static final String SCHEME_STREAM = "stream";
private static final String STREAM_URI_PREFIX = SCHEME_STREAM + "://";
public StreamImageDownloader(Context context) {
super(context);
}
#Override
protected InputStream getStreamFromOtherSource(String imageUri, Object extra) throws IOException {
if (imageUri.startsWith(STREAM_URI_PREFIX)) {
return (InputStream) extra;
} else {
return super.getStreamFromOtherSource(imageUri, extra);
}
}
}
So if anyone can help me create a better CustomImageDecoder that handles a BASE64 encoded string, or a byte[] containing an image so I can use decodeByteArray, I would be grateful!
Thank you.
UnversalImageLoader uses the following schemes to decode the files
"h t t p ://site.com/image.png" // from Web
"file:///mnt/sdcard/image.png" // from SD card
"file:///mnt/sdcard/video.mp4" // from SD card (video thumbnail)
"content://media/external/images/media/13" // from content provider
"content://media/external/video/media/13" // from content provider (video thumbnail)
"assets://image.png" // from assets
"drawable://" + R.drawable.img // from drawables (non-9patch images)
your scheme is stream://
Hope that helps.
Just to close this off:
The issue here is actually a bug in Android <4.3 where Android can't display images that either aren't closed properly (missing end bytes) or contain certain metadata that, for some reason, it doesn't like. I'm not sure what metadata this is, however. My issue was with JPEGs not being terminated properly.
The bug is fixed in Android 4.3 anyway.
I am working on an application (Android 4.4 -- API 20) where I am generating a report in HTML format. I use the WebView object to display the report in my app.
What I would like to be able to do is convert this WebView into a pdf document.
I have been able to convert it using PdfDocument, and doing .draw onto the page from the WebView object. I save the file, and this works, except that the result is a single page document. There are no page breaks.
View content = (View) webView;
PrintAttributes pdfPrintAttrs = new PrintAttributes.Builder().
setColorMode(PrintAttributes.COLOR_MODE_MONOCHROME).
setMediaSize(PrintAttributes.MediaSize.NA_LETTER.asLandscape()).
setResolution(new Resolution("zooey", PRINT_SERVICE, 300, 300)).
setMinMargins(PrintAttributes.Margins.NO_MARGINS).
build();
PdfDocument document = new PrintedPdfDocument(mContext,pdfPrintAttrs);
PageInfo pageInfo = new PageInfo.Builder(webView.getMeasuredWidth(), webView.getContentHeight(), 1).create();
Page page = document.startPage(pageInfo);
content.draw(page.getCanvas());
document.finishPage(page);
If I change it so that I use the PrintedPdfDocumet and don't specify the PageInfo I only get the viewable part of the WebView object.
View content = (View) webView;
PrintAttributes pdfPrintAttrs = new PrintAttributes.Builder().
setColorMode(PrintAttributes.COLOR_MODE_MONOCHROME).
setMediaSize(PrintAttributes.MediaSize.NA_LETTER.asLandscape()).
setResolution(new Resolution("zooey", PRINT_SERVICE, 300, 300)).
setMinMargins(PrintAttributes.Margins.NO_MARGINS).
build();
PrintedPdfDocument document = new PrintedPdfDocument(mContext,pdfPrintAttrs);
Page page = document.startPage(0);
content.draw(page.getCanvas());
document.finishPage(page);
If I use the PrintManager and create a print adapter from the WebView object with createPrintDocumentAdapter, I can select the "Save as PDF" option and the resulting pdf file has the page breaks as I specify in the CSS of the original web page.
PrintManager printManager = (PrintManager) getSystemService(Context.PRINT_SERVICE);
PrintDocumentAdapter printAdapter = webView.createPrintDocumentAdapter();
String jobName = getString(R.string.app_name) + " Report "
+ reportName;
PrintAttributes printAttrs = new PrintAttributes.Builder().
setColorMode(PrintAttributes.COLOR_MODE_MONOCHROME).
setMediaSize(PrintAttributes.MediaSize.NA_LETTER.asLandscape()).
setMinMargins(PrintAttributes.Margins.NO_MARGINS).
build();
PrintJob printJob = printManager.print(jobName, printAdapter,
printAttrs);
My question is: can I specify that I want the PrintManager to perform a "Save as PDF" and provide the name and location of the resulting file so that there is no interaction with the user?
Or: Is there a way I can convert my WebView object into a PDF and allow for page breaks.
It might be a late answer but I was also in need of similar solution with Print Framework so far, and I splitted the Pdf Document into pages with the code below.
As far as I can see, you cannot really make the WebView or Pdf Document splits your pdf file into pages in a smart way (not cutting the text or image). But what we can do is to create Pages in a ratio of A4 or Letter size, so it can fit into print out paper format.
But there is another issue I'm facing. The code below works as expected in Android 4.4 but not in later versions. In Android-L, only the visible part of WebView is drawn into Pdf File, but white blank pages for the rest of the HTML in WebView.
According to documentation,
public static void enableSlowWholeDocumentDraw ()
For apps targeting the L release, WebView has a new default behavior that reduces memory footprint and increases performance by intelligently choosing the portion of the HTML document that needs to be drawn. These optimizations are transparent to the developers. However, under certain circumstances, an App developer may want to disable them:
When an app uses onDraw(Canvas) to do own drawing and accesses portions of the page that is way outside the visible portion of the page.
When an app uses capturePicture() to capture a very large HTML document. Note that capturePicture is a deprecated API.
Enabling drawing the entire HTML document has a significant performance cost. This method should be called before any WebViews are created.
I've created a Bug Report, and commented on a similar bug report HERE, but no response so far. But until then, you can use the code below.
/**
* Creates a PDF Multi Page Document depending on the Ratio of Letter Size.
* This method does not close the Document. It should be Closed after writing Pdf Document to a File.
*
* #return
*/
private PdfDocument createMultiPagePdfDocument(int webViewWidth, int webViewHeight) {
/* Find the Letter Size Height depending on the Letter Size Ratio and given Page Width */
int letterSizeHeight = getLetterSizeHeight(webViewWidth);
PdfDocument document = new PrintedPdfDocument(getActivity(), getPrintAttributes());
final int numberOfPages = (webViewHeight/letterSizeHeight) + 1;
for (int i = 0; i < numberOfPages; i++) {
int webMarginTop = i*letterSizeHeight;
PdfDocument.PageInfo pageInfo = new PdfDocument.PageInfo.Builder(webViewWidth, letterSizeHeight, i+1).create();
PdfDocument.Page page = document.startPage(pageInfo);
/* Scale Canvas */
page.getCanvas().translate(0, -webMarginTop);
mWebView.draw(page.getCanvas());
document.finishPage(page);
}
return document;
}
/**
* Calculates the Letter Size Paper's Height depending on the LetterSize Dimensions and Given width.
*
* #param width
* #return
*/
private int getLetterSizeHeight(int width) {
return (int)((float)(11*width)/8.5);
}
Not sure if this will solve your page-break issues, but have you considered using the open-source wkHTMLtoPDF library (http://wkhtmltopdf.org/) for the conversion from HTML to PDF? We have used it extensively by creating a micro-service that we pass the HTML code to, then have the service convert it to PDF and return the link to the PDF, or alternatively have it return the PDF (depending on size). I know using an external service for the conversion might be a pain (or maybe you don't have internet access from the device), but if that's not an issue, then this could be an option. There may be other APIs available to do this conversion as well. One such API is Neutrino API. There are many others - you can search for APIs using one of these API search engines:
apis.io
Progammable Web
Public APIs
After spending enormous time with this problem, I used DexMaker to implement non public abstract callbacks and came up with this:
#Override
protected void onPreExecute() {
super.onPreExecute();
printAdapter = webView.createPrintDocumentAdapter();
}
#Override
protected Void doInBackground(Void... voids) {
File file = new File(pdfPath);
if (file.exists()) {
file.delete();
}
try {
file.createNewFile();
// get file descriptor
descriptor = ParcelFileDescriptor.open(file, ParcelFileDescriptor.MODE_READ_WRITE);
// create print attributes
PrintAttributes attributes = new PrintAttributes.Builder()
.setMediaSize(PrintAttributes.MediaSize.ISO_A4)
.setResolution(new PrintAttributes.Resolution("id", PRINT_SERVICE, 300, 300))
.setColorMode(PrintAttributes.COLOR_MODE_COLOR)
.setMinMargins(new PrintAttributes.Margins(0, 0, 0, 0))
.build();
ranges = new PageRange[]{new PageRange(1, numberPages)};
// dexmaker cache folder
cacheFolder = new File(context.getFilesDir() +"/etemp/");
printAdapter.onStart();
printAdapter.onLayout(attributes, attributes, new CancellationSignal(), getLayoutResultCallback(new InvocationHandler() {
#Override
public Object invoke(Object o, Method method, Object[] objects) throws Throwable {
if (method.getName().equals("onLayoutFinished")) {
onLayoutSuccess();
} else {
Log.e(TAG, "Layout failed");
pdfCallback.onPdfFailed();
}
return null;
}
}, cacheFolder), new Bundle());
} catch (IOException e) {
e.printStackTrace();
Log.e(TAG, e != null ? e.getMessage() : "PrintPdfTask unknown error");
}
return null;
}
private void onLayoutSuccess() throws IOException {
PrintDocumentAdapter.WriteResultCallback callback = getWriteResultCallback(new InvocationHandler() {
#Override
public Object invoke(Object o, Method method, Object[] objects) throws Throwable {
if (method.getName().equals("onWriteFinished")) {
pdfCallback.onPdfCreated();
} else {
Log.e(TAG, "Layout failed");
pdfCallback.onPdfFailed();
}
return null;
}
}, cacheFolder);
printAdapter.onWrite(ranges, descriptor, new CancellationSignal(), callback);
}
/**
* Implementation of non public abstract class LayoutResultCallback obtained via DexMaker
* #param invocationHandler
* #param dexCacheDir
* #return LayoutResultCallback
* #throws IOException
*/
public static PrintDocumentAdapter.LayoutResultCallback getLayoutResultCallback(InvocationHandler invocationHandler,
File dexCacheDir) throws IOException {
return ProxyBuilder.forClass(PrintDocumentAdapter.LayoutResultCallback.class)
.dexCache(dexCacheDir)
.handler(invocationHandler)
.build();
}
/**
* Implementation of non public abstract class WriteResultCallback obtained via DexMaker
* #param invocationHandler
* #param dexCacheDir
* #return LayoutResultCallback
* #throws IOException
*/
public static PrintDocumentAdapter.WriteResultCallback getWriteResultCallback(InvocationHandler invocationHandler,
File dexCacheDir) throws IOException {
return ProxyBuilder.forClass(PrintDocumentAdapter.WriteResultCallback.class)
.dexCache(dexCacheDir)
.handler(invocationHandler)
.build();
}
Abstract:
reading images from file
with toggled bits to make unusable for preview tools
cant use encryption, to much power needed
can I either optimize the code below, or is there a better approach
Longer description:
I am trying to improve my code, maybe you got some ideas or improvements for the following situation. Please be aware that I neither try to beat the CIA, nor care much if somebody "brakes" the encryption.
The background is simple: My app loads a bunch of images from a server into a folder on the SD card. I do NOT want the images to be simple JPG files, because in this case the media indexer would list them in the library, and a user could simply copy the whole folder to his harddrive.
The obvious way to go is encryption. But a full blown AES or other encryption does not make sense, for two reasons: I would have to store the passkey in the app, so anyone could get the key with some effort anyway. And the price for decrypting images on the fly is way too high (we are talking about e.g. a gallery with 30 200kB pictures).
So I decided to toggle some bits in the image. This makes the format unreadable for image tools (or previews), but is pretty easy undone when reading the images. For "encrypting" I use some C# tool, the "decrypt" lines are the following ones:
public class CustomInputStream extends InputStream {
private String _fileName;
private BufferedInputStream _stream;
public CustomInputStream(String fileName) {
_fileName = fileName;
}
public void Open() throws IOException {
int len = (int) new File(_fileName).length();
_stream = new BufferedInputStream(new FileInputStream(_fileName), len);
}
#Override
public int read() throws IOException {
int value = _stream.read() ^ (1 << 7);
return value;
}
#Override
public void close() throws IOException {
_stream.close();
}
}
I tried overwriting the other methods (read with more then one byte) too, but this kills the BitmapFactory - not sure why, maybe I did something wrong. Here is the code for the image bitmap creation:
Bitmap bitmap = null;
try {
InputStream i = CryptoProvider.GetInstance().GetDecoderStream(path);
bitmap = BitmapFactory.decodeStream(i);
i.close();
} catch (Exception e1) {
_logger.Error("Cant load image " + path + " ERROR " + e1);
}
if (bitmap == null) {
_logger.Error("Image is NULL for path " + path);
}
return bitmap;
Do you have any feedback on the chosen approach? Any way to optimize it, or a completely different approach for Android devices?
You could try XORing the bytestream with the output of a fast PRNG. Just use a different seed for each file and you're done.
note: As already noted in the question, such methods are trivial to bypass.
I have the following problem:
suppose that until now, I am using R.drawable.img to set the image in some imageviews
with
imgView.setImage(aProduct.getImgId());
the simplified product class look like this:
class Product{
int imgId;
....
public void setImgId(int id){
this.imgId=id;
}
public int getImgId(){
return this.imgId
}
...
}
my application is now "evolved" because the user can add customized products
taking the img from the camera and getting the Uri of the picture.
and to set the image on the ImageView imgView.setImgURI(Uri)
Now my question is:
what would be the best approach to have a mixed int/Uri image resources ambient?
can I obtain the Uri of a "R.drawable.img"?
I'm not sure if my question is clear, I mean:
I have to check, before to set the imageview, if my product has an Uri or an int Id,
and then make an "if" to call the appropriate method, or there is a simpler solution?
Thank you for reading, and sorry for my english.
Regards.
Your problem is that there are basically 3 types of image resources:
R.id... resources: internal resources, such as icons you put into the res folder
content URI's: local files or content provider resources such as content:// or file:///sdcard/...
remote file URL's: images on the web, such as http://...
You are looking for a way to pass around one identifier that can deal with all three. My solution was to pass around a string: either the toString() of the URI's, or just the string respresentation of the R.id integer.
I'm using the following code, for example, to deal with this and make the code work with it:
public static FastBitmapDrawable returnAndCacheCover(String cover, ImageRepresentedProductArtworkCreator artworkCreator) {
Bitmap bitmap = null;
Uri coverUri = null;
boolean mightBeUri = false;
//Might be a resId. Needs to be cached. //TODO: problem: resId of default cover may not survive across versions of the app.
try {
bitmap = BitmapFactory.decodeResource(Collectionista.getInstance().getResources(), Integer.parseInt(cover));
} catch (NumberFormatException e) {
//Not a resId after all.
mightBeUri=true;
}
if(bitmap==null || mightBeUri){
//Is not a resId. Might be a contentUri.
try {
coverUri = Uri.parse(cover);
} catch (NullPointerException ne) {
//Is null
return null;
}
}
if(coverUri!=null){
if(coverUri.getScheme().equals("content")){
//A contentUri. Needs to be cached.
try {
bitmap = MediaStore.Images.Media.getBitmap(Collectionista.getInstance().getContentResolver(), coverUri);
} catch (FileNotFoundException e) {
return null;
} catch (IOException e) {
return null;
}
}else{
//Might be a web uri. Needs to be cached.
bitmap = loadCoverFromWeb(cover);
}
}
return new FastBitmapDrawable(bitmap);
}
You might be interested to take over the logic part. Ofcourse cover is the string in question here.
Forget android.resource:// as a replacement for the R.id... integer. Claims are going round it does not work: http://groups.google.com/group/android-developers/browse_thread/thread/a672d71dd7df4b2d
To find out how to implement loadCoverFromWeb, have a look around in other questions or ping me. This web stuff is kind of a field of it's own.
(Based on GPLv3 code out of my app Collectionista: https://code.launchpad.net/~pjv/collectionista/trunk)