Develop Reference

Dealing with large bitmap onPictureTaken android

My app is an OCR app base on Tesseract. It will do OCR task from camera picture. Users can take many pictures and put them into an OCR queue. To get more accuracy, I want to keep high quality image (I choose min size is 1024 x 768 (maybe larger in future), JPEG, 100% quality). When users take many pictures, there are three things to do:
Save the image data byte[] to file and correct EXIF.
Correct the image orientation base on device's orientation. I know there are some answers that said the image which comes out of the camera is not oriented automatically, have to correct it from file, like here and here. I'm not sure about it, I can setup the camera preview orientation correctly, but the image results aren't correct.
Load bitmap from taken picture, convert it to grayscale and save to another file for OCR task.
And here is my try:
public static boolean saveBitmap(byte[] bitmapData, int orientation, String imagePath, String grayScalePath) throws Exception {
Boolean rotationSuccess = false;
BitmapFactory.Options options = new BitmapFactory.Options();
options.inPreferredConfig = Bitmap.Config.ARGB_8888;
Bitmap originalBm = null;
Bitmap bitmapRotate = null;
Bitmap grayScale = null;
FileOutputStream outStream = null;
try {
// save directly from byte[] to file
saveBitmap(bitmapData, imagePath);
// down sample
options.inJustDecodeBounds = true;
BitmapFactory.decodeFile(imagePath, options);
int sampleSize = calculateInSampleSize(options, Config.CONFIG_IMAGE_WIDTH, Config.CONFIG_IMAGE_HEIGHT);
options.inJustDecodeBounds = false;
options.inSampleSize = sampleSize;
originalBm = BitmapFactory.decodeFile(imagePath, options);
Matrix mat = new Matrix();
mat.postRotate(orientation);
bitmapRotate = Bitmap.createBitmap(originalBm, 0, 0, originalBm.getWidth(), originalBm.getHeight(), mat, true);
originalBm.recycle();
originalBm = null;
outStream = new FileOutputStream(new File(imagePath));
bitmapRotate.compress(CompressFormat.JPEG, 100, outStream);
// convert to gray scale
grayScale = UIUtil.convertToGrayscale(bitmapRotate);
saveBitmap(grayScale, grayScalePath);
grayScale.recycle();
grayScale = null;
bitmapRotate.recycle();
bitmapRotate = null;
rotationSuccess = true;
} catch (OutOfMemoryError e) {
e.printStackTrace();
System.gc();
} finally {
if (originalBm != null) {
originalBm.recycle();
originalBm = null;
}
if (bitmapRotate != null) {
bitmapRotate.recycle();
bitmapRotate = null;
}
if (grayScale != null) {
grayScale.recycle();
grayScale = null;
}
if (outStream != null) {
try {
outStream.close();
} catch (IOException e) {
}
outStream = null;
}
}
Log.d(TAG,"save completed");
return rotationSuccess;
}
Save to file directly from byte[]
public static void saveBitmap(byte[] bitmapData, String fileName) throws Exception {
File file = new File(fileName);
FileOutputStream fos;
BufferedOutputStream bos = null;
try {
final int bufferSize = 1024 * 4;
fos = new FileOutputStream(file);
bos = new BufferedOutputStream(fos, bufferSize);
bos.write(bitmapData);
bos.flush();
} catch (Exception ex) {
throw ex;
} finally {
if (bos != null) {
bos.close();
}
}
}
Calculate scale size
public static int calculateInSampleSize(BitmapFactory.Options options, int reqWidth, int reqHeight) {
// Raw height and width of image
final int height = options.outHeight;
final int width = options.outWidth;
int inSampleSize = 1;
if (height > reqHeight || width > reqWidth) {
final int halfHeight = height / 2;
final int halfWidth = width / 2;
// Calculate the largest inSampleSize value that is a power of 2 and
// keeps both
// height and width larger than the requested height and width.
while ((halfHeight / inSampleSize) > reqHeight && (halfWidth / inSampleSize) > reqWidth) {
inSampleSize *= 2;
}
}
return inSampleSize;
}
When save complete, this image is loaded into thumbnail image view by UIL. The problem is the save task is very slow (wait some second before save complete and load into view), and sometime I got OutOfMemory exception. Is there any ideas to reduce the save task and avoid OutOfMemory exception?
Any help would be appreciated!
P/S: the first time I try to convert byte[] to bitmap instead of save to file, and then rotate and convert to grayscale, but I still got above issues.
Update: here is the grayscale bitmap process:
public static Bitmap convertToGrayscale(Bitmap bmpOriginal) {
int width, height;
height = bmpOriginal.getHeight();
width = bmpOriginal.getWidth();
Bitmap bmpGrayscale = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
Canvas c = new Canvas(bmpGrayscale);
Paint paint = new Paint();
ColorMatrix cm = new ColorMatrix();
cm.setSaturation(0);
ColorMatrixColorFilter f = new ColorMatrixColorFilter(cm);
paint.setColorFilter(f);
c.drawBitmap(bmpOriginal, 0, 0, paint);
return bmpGrayscale;
}
The OutOfMemory exception seldom occurred (just a few times) and I can't reproduce it now.

Update:
Since you're still saying that the method takes too long time I would define a callback interface
interface BitmapCallback {
onBitmapSaveComplete(Bitmap bitmap, int orientation);
onBitmapRotateAndBWComlete(Bitmap bitmap);
}
Let your activity implement the above interface and convert the byte[] to bitmap in top of your saveBitmap method and fire the callback, before the first call to save. Rotate the imageView based on the orientation parameter and set a black/white filter on the imageView to fool the user into thinking that the bitmap is black and white (do this in your activity). See to that the calls are done on main thread (the calls to imageView). Keep your old method as you have it. (all steps need to be done anyway) Something like:
public static boolean saveBitmap(byte[] bitmapData, int orientation, String imagePath, String grayScalePath, BitmapCallback callback) throws Exception {
Boolean rotationSuccess = false;
BitmapFactory.Options options = new BitmapFactory.Options();
options.inPreferredConfig = Bitmap.Config.ARGB_8888;
Bitmap originalBm = null;
Bitmap bitmapRotate = null;
Bitmap grayScale = null;
FileOutputStream outStream = null;
try {
// TODO: convert byte to Bitmap, see to that the image is not larger than your wanted size (1024z768)
callback.onBitmapSaveComplete(bitmap, orientation);
// save directly from byte[] to file
saveBitmap(bitmapData, imagePath);
.
.
// same as old
.
.
saveBitmap(grayScale, grayScalePath);
// conversion done callback with the real fixed bitmap
callback.onBitmapRotateAndBWComlete(grayScale);
grayScale.recycle();
grayScale = null;
bitmapRotate.recycle();
bitmapRotate = null;
rotationSuccess = true;
How do you setup your camera? What might be causing the long execution time in the first saveBitmap call, could be that you are using the default camera picture size settings and not reading the supported camera picture size and choosing best fit for your 1024x768 image needs. You might be taking big mpixel images and saving such, but in the end need you need < 1 mpixles (1024x768). Something like this in code:
Camera camera = Camera.open();
Parameters params = camera.getParameters();
List sizes = params.getSupportedPictureSizes();
// Loop camera sizes and find best match, larger than 1024x768
This is probably where you will save most of the time if you are not doing this already. And do it only once, during some initialization phase.
Increase the buffer to 8k in saveBitmap, change the 1024*4 to 1024*8, this would increase the performance at least, not save any significant time perhaps.
To save/reuse bitmap memory consider using inBitmap field, if you have a post honeycomb version, of BitmapFactory.Options and set that field to point to bitmapRotate bitmap and send options down to your convertToGrayscale method to not need allocating yet another bitmap down in that method. Read about inBitmap here: inBitmap

Out of memory when processing multiple large bitmaps

In the app I'm working on, part of the user's input is a series of images. Some of these might be 4MB large in their raw form. I resize and rotate them, then save them in the app's portion of the device memory for later use. The problem I'm experiencing is that I seem to run out of memory even though I recycle each Bitmap after it's saved.
Here's the main processing
private class SaveImagesTask extends AsyncTask<Long, Void, Void>{
#Override
protected Void doInBackground(Long... ids){
long id = ids[0];
Iterator<ImageButton> itImg = arrBtnImage.iterator();
Iterator<TextView> itLbl = arrLblImage.iterator();
while(itImg.hasNext() && itLbl.hasNext()){
String imgPath = (String) itImg.next().getTag();
String imgLbl = itLbl.next().getText().toString().trim();
String imgName = imgLbl.replace(" ", "_").replace(",", "_");
imgName += ".jpg";
if(imgPath != null){
/* Save resized version of image */
File dir = getApplicationContext().getFilesDir();
dir = new File(dir, "temp/" + Long.toString(plantId));
boolean madeDir = dir.mkdirs();
File path = new File(dir, imgName);
Bitmap toSave = getScaledBitmap(imgPath, IMAGE_MAX_SIDE_LENGTH, IMAGE_MAX_SIDE_LENGTH);
try{
BufferedOutputStream outStream = new BufferedOutputStream(new FileOutputStream(path));
boolean insertSuccess = toSave.compress(Bitmap.CompressFormat.JPEG, 90, outStream);
outStream.close();
}
catch(FileNotFoundException e){
e.printStackTrace();
}
catch(IOException e){
e.printStackTrace();
}
toSave.recycle();
}//if
}//while(more images to process)
}// method: doInBackground(params)
}// inner class: saveImages extends AsyncTask
And here's where I resize the image
private Bitmap getScaledBitmap(String picturePath, int newWidth, int newHeight){
/* Size */
BitmapFactory.Options sizeOptions = new BitmapFactory.Options();
sizeOptions.inJustDecodeBounds = true;
BitmapFactory.decodeFile(picturePath, sizeOptions);
int sampleSize = 1;
int rawHeight = sizeOptions.outHeight;
int rawWidth = sizeOptions.outWidth;
if(rawHeight > newHeight || rawWidth > newWidth){
/* Find the dimension that needs to change the most */
int heightRatio = Math.round((float) rawHeight / (float) newHeight);
int widthRatio = Math.round((float) rawWidth / (float) newWidth);
sampleSize = (heightRatio > widthRatio ? heightRatio : widthRatio);
}//if(raw image is wider or taller than it should be){reduce size so neither is too large}
sizeOptions.inJustDecodeBounds = false;//Load pixels for display.
sizeOptions.inSampleSize = sampleSize;//Set shrink factor.
Bitmap scaledBitmap = BitmapFactory.decodeFile(picturePath, sizeOptions);
/* Rotation */
int rotation = 1;
try{
ExifInterface exif = new ExifInterface(picturePath);
rotation = exif.getAttributeInt(ExifInterface.TAG_ORIENTATION, ExifInterface.ORIENTATION_NORMAL);
}
catch(IOException e){
e.printStackTrace();
}
int rotationInDegrees = 0;
if(rotation == ExifInterface.ORIENTATION_ROTATE_90)
rotationInDegrees = 90;
else if(rotation == ExifInterface.ORIENTATION_ROTATE_180)
rotationInDegrees = 180;
else if(rotation == ExifInterface.ORIENTATION_ROTATE_270)
rotationInDegrees = 270;
Matrix matrix = new Matrix();
if(rotation != 0f)
matrix.preRotate(rotationInDegrees);
return Bitmap.createBitmap(scaledBitmap, 0, 0,
scaledBitmap.getWidth(), scaledBitmap.getHeight(), matrix, true);
}// method: getScaledBitmap(String, int, int)
Before I start getting comments about this being so common of a question, I'll point out that I'm not displaying these images, so it's not like I'm trying to keep all of these in memory. I need to keep large images because users will want to be able to zoom in on the pictures, but I'm resizing them because they don't need to be ridiculously huge. Pretty much any other solution I've seen on SO for images and OOM errors don't apply to my back-to-back access of multiple images.
So like I said, I'm recycling each Bitmap after it's saved, but they still seem to be using memory. Any idea what I'm missing?

You're not recycling scaledBitmap in getScaledBitmap. Fixing that should help. Change this line:
return Bitmap.createBitmap(scaledBitmap, 0, 0,
scaledBitmap.getWidth(), scaledBitmap.getHeight(), matrix, true);
to something like:
Bitmap newBitmap = Bitmap.createBitmap(scaledBitmap, 0, 0,
scaledBitmap.getWidth(), scaledBitmap.getHeight(), matrix, true);
scaledBitmap.recycle();
return newBitmap;

If you have multiple threads working on large bitmaps, you will use a lot of memory on some cases.
What you need is to find the best approach according to your needs. here are some things you can do and/or need to know:
use a single thread for the images handling.
always recycle old bitmaps that you don't need anymore, as soon as possible. it's true that the GC will help you, but that can help it too, and it will work even on pre-honeycomb devices.
do the image manipulations via NDK (so you won't need to have 2 bitmaps for each image manipulation), for example using this.
downsample the image to the minimal size that you need, and never assume that the memory is large enough for any given image (unless you are 100% sure that the images are small).
remember that the requirements for android devices are still very low in terms of RAM per app (heap size) - the bare minimal is still 16MB per app.
you can use android:largeHeap="true" in the manifest, but that doesn't mean anything about how much more you will get, if at all.

image rotation not working on Samsung Galaxy Nexus android

I've tested this code snippet on about 25 devices and it works great on all of them except a Samsung Galaxy Nexus that I'm trying to test with now.
Here is the method and I apologize for not trimming it down to find the exact spot that's throwing the exception, but eclipse's debugging is doodoo.
private void setupImageView() {
imageLocation = currentPhotoPath;
// Get the dimensions of the View
Display display = getWindowManager().getDefaultDisplay();
Point size = getDisplaySize(display);
int targetW = size.x;
// Get the dimensions of the bitmap
BitmapFactory.Options bmOptions = new BitmapFactory.Options();
bmOptions.inJustDecodeBounds = true;
BitmapFactory.decodeFile(imageLocation, bmOptions);
int photoW = bmOptions.outWidth;
int photoH = bmOptions.outHeight;
// Determine how much to scale down the image
int scaleFactor = Math.min(photoW / targetW, photoH / targetW);
// Decode the image file into a Bitmap sized to fill the View
bmOptions.inJustDecodeBounds = false;
bmOptions.inSampleSize = scaleFactor;
bmOptions.inPurgeable = true;
Bitmap bitmap = BitmapFactory.decodeFile(imageLocation, bmOptions);
//int rotationForImage = getRotationForImage(imageLocation);
int rotationForImage = (whichCamera == 0 ? 90 : 270);
if (rotationForImage != 0) {
int targetWidth = rotationForImage == 90 || rotationForImage == 270 ? bitmap.getHeight() : bitmap.getWidth();
int targetHeight = rotationForImage == 90 || rotationForImage == 270 ? bitmap.getWidth() : bitmap.getHeight();
Bitmap rotatedBitmap = Bitmap.createBitmap(targetWidth, targetHeight, bitmap.getConfig());
Canvas canvas = new Canvas(rotatedBitmap);
Matrix matrix = new Matrix();
matrix.setRotate(rotationForImage, bitmap.getWidth() / 2, bitmap.getHeight() / 2);
canvas.drawBitmap(bitmap, matrix, new Paint());
bitmap.recycle();
bitmap = rotatedBitmap;
ByteArrayOutputStream bytes = new ByteArrayOutputStream();
bitmap.compress(Bitmap.CompressFormat.JPEG, 40, bytes);
try
{
File f = new File(imageLocation);
f.createNewFile();
//write the bytes in file
FileOutputStream fo = new FileOutputStream(f);
fo.write(bytes.toByteArray());
fo.close();
}
catch(java.io.IOException e){}
}
imageView.setImageBitmap(bitmap);
}
anyone know what Samsung does differently with the nexus that would cause this to throw an exception? It works fine on a Galaxy S III

It looks like something in the if block you mention is throwing an NPE - that's the real bug here. Don't worry about the Activity/ResultInfo stuff, that is downstream and triggered by the NPE. Go line by line and look for the null reference :-)
Regarding Eclipse - sadly I don't have much experience there. For Android I personally use IntelliJ and the debugging works well. Are you able to debug other Java code (even a simple Hello, World)?

Android bitmap size exceeds VM budget error

Android bitmap size exceeds VM budget.
My app is getting this error frequently. I have two questions.
Do I need to recycle my about activity (it contains some imageviews and buttons and textViews)?
What is the difference between .recycle(); and between system.gc(); ?

You should always try and recycle Bitmaps afte you have used them.
As far as I understand, you should try and avoid calling system.gc().
Calling recycle() will allow the bitmap object to be garbage collected.
I hope this helps.

I got the same problem while picking images from camera.
I resized the bitmap of image using following code:
Bitmap bitmap = resizeBitMapImage(picturePath, 75, 91);
profilePic.setImageBitmap(bitmap);
private Bitmap resizeBitMapImage(String filePath, int targetWidth,
int targetHeight) {
Bitmap bitMapImage = null;
// First, get the dimensions of the image
Options options = new Options();
options.inJustDecodeBounds = true;
BitmapFactory.decodeFile(filePath, options);
double sampleSize = 0;
// Only scale if we need to
// (16384 buffer for img processing)
Boolean scaleByHeight = Math.abs(options.outHeight - targetHeight) >= Math
.abs(options.outWidth - targetWidth);
if (options.outHeight * options.outWidth * 2 >= 1638) {
// Load, scaling to smallest power of 2 that'll get it <= desired
// dimensions
sampleSize = scaleByHeight ? options.outHeight / targetHeight
: options.outWidth / targetWidth;
sampleSize = (int) Math.pow(2d,
Math.floor(Math.log(sampleSize) / Math.log(2d)));
}
// Do the actual decoding
options.inJustDecodeBounds = false;
options.inTempStorage = new byte[128];
while (true) {
try {
options.inSampleSize = (int) sampleSize;
bitMapImage = BitmapFactory.decodeFile(filePath, options);
break;
} catch (Exception ex) {
try {
sampleSize = sampleSize * 2;
} catch (Exception ex1) {
}
}
}
return bitMapImage;
}

Does "Bitmap.createScaledBitmap" convert an 32 bit image into 24 bit?

In my app I load an image as 32 bit (ARGB_8888) this way:
Bitmap.Config mBitmapConfig;
mBitmapConfig = Bitmap.Config.ARGB_8888;
BitmapFactory.Options options = new BitmapFactory.Options();
options.inPreferredConfig = mBitmapConfig;
mBitmap = BitmapFactory.decodeFile(SourceFileName, options);
Then scale:
mBitmap = Bitmap.createScaledBitmap(mBitmap, iW, iH, true);
If I use for scaling the same Width and Height of the original bitmap, it is 1/2 of the size in megabytes (I'm watching the heap size).
Changing the value "ARGB_8888" to "RGB_565" (24 bit) gives the same size in megabytes after scaling.
Can someone explain this phenomenon and may be give me an advice, how to scale bitmaps in 32 bit color space?
Thanks!

I looked up the method createScaledBitmap in the source for the Bitmap class (Link):
public static Bitmap createScaledBitmap(Bitmap src, int dstWidth,
int dstHeight, boolean filter) {
Matrix m;
synchronized (Bitmap.class) {
// small pool of just 1 matrix
m = sScaleMatrix;
sScaleMatrix = null;
}
if (m == null) {
m = new Matrix();
}
final int width = src.getWidth();
final int height = src.getHeight();
final float sx = dstWidth / (float)width;
final float sy = dstHeight / (float)height;
m.setScale(sx, sy);
Bitmap b = Bitmap.createBitmap(src, 0, 0, width, height, m, filter);
synchronized (Bitmap.class) {
// do we need to check for null? why not just assign everytime?
if (sScaleMatrix == null) {
sScaleMatrix = m;
}
}
return b;
}
And the call to createBitmap() should return your unchanged source bitmap due to this check in the method body:
if (!source.isMutable() && x == 0 && y == 0 && width == source.getWidth() &&
height == source.getHeight() && (m == null || m.isIdentity())) {
return source;
}
Looking at just this it would seem that your original bitmap is returned, But, if your bitmap happens to be mutable, you effectively skip this check and end up here:
if (m == null || m.isIdentity()) {
bitmap = createBitmap(neww, newh,
source.hasAlpha() ? Config.ARGB_8888 : Config.RGB_565);
paint = null; // not needed
}
As you are not performing any scaling, your matrix will be the identity matrix, and the condition is satisfied. The bitmap created is, as you can see, dependent on the alpha in the source bitmap. If no alpha is present, you end up with a result bitmap with the RGB_565 format rather than the ARGB_8888.
So, to scale and preserve the 32-bit format, your bitmap should either be immutable or use an Alpha channel.

Color Banding Solved ooooooooooyyyyyyyeaaaaaaaaaa
I solved color banding in two phases
1) * when we use the BitmapFactory to decode resources it decodes the resource in RGB565 which shows color banding, instead of using ARGB_8888, so i used BitmapFactory.Options for setting the decode options to ARGB_8888
second problem was whenever i scaled the bitmap it again got banded
2) This was the tough part and took a lot of searching and finally worked
* the method Bitmap.createScaledBitmap for scaling bitmaps also reduced the images to RGB565 format after scaling i got banded images(the old method for solving this was using at least one transparent pixel in a png but no other format like jpg or bmp worked)so here i created a method CreateScaledBitmap to scale the bitmap with the original bitmaps configurations in the resulting scale bitmap(actually i copied the method from a post by logicnet.dk and translated in java)
BitmapFactory.Options myOptions = new BitmapFactory.Options();
myOptions.inDither = true;
myOptions.inScaled = false;
myOptions.inPreferredConfig = Bitmap.Config.ARGB_8888;//important
//myOptions.inDither = false;
myOptions.inPurgeable = true;
Bitmap tempImage =
BitmapFactory.decodeResource(getResources(),R.drawable.defaultart, myOptions);//important
//this is important part new scale method created by someone else
tempImage = CreateScaledBitmap(tempImage,300,300,false);
ImageView v = (ImageView)findViewById(R.id.imageView1);
v.setImageBitmap(tempImage);
// the function
public static Bitmap CreateScaledBitmap(Bitmap src, int dstWidth, int dstHeight, boolean filter)
{
Matrix m = new Matrix();
m.setScale(dstWidth / (float)src.getWidth(), dstHeight / (float)src.getHeight());
Bitmap result = Bitmap.createBitmap(dstWidth, dstHeight, src.getConfig());
Canvas canvas = new Canvas(result);
Paint paint = new Paint();
paint.setFilterBitmap(filter);
canvas.drawBitmap(src, m, paint);
return result;
}
Please correct me if i am wrong.
Also comment if it worked for you.
I am so happy i solved it, Hope it works for you.

It's easy to create your own version that keeps the pixel format of the source:
public static Bitmap CreateScaledBitmap(Bitmap src, int dstWidth, int dstHeight, bool filter)
{
var m = new Matrix();
m.SetScale(dstWidth / (float)src.Width, dstHeight / (float)src.Height);
var result = Bitmap.CreateBitmap(dstWidth, dstHeight, src.GetConfig());
using (var canvas = new Canvas(result))
{
var paint = new Paint();
paint.FilterBitmap = filter;
canvas.DrawBitmap(src, m, paint);
}
return result;
}
(Code is for Monodroid, but it should be easy to translate to Java)

I assume you are writing code for a version of Android lower than 3.2 (API level < 12), because since then the behavior of the methods
BitmapFactory.decodeFile(pathToImage);
BitmapFactory.decodeFile(pathToImage, opt);
bitmapObject.createScaledBitmap(bitmap, desiredWidth, desiredHeight, false /*filter?*/);
has changed.
On older platforms (API level < 12) the BitmapFactory.decodeFile(..) methods try to return a Bitmap with RGB_565 config by default, if they can't find any alpha, which lowers the quality of an iamge. This is still ok, because you can enforce an ARGB_8888 bitmap using
options.inPrefferedConfig = Bitmap.Config.ARGB_8888
options.inDither = false
The real problem comes when each pixel of your image has an alpha value of 255 (i.e. completely opaque). In that case the Bitmap's flag 'hasAlpha' is set to false, even though your Bitmap has ARGB_8888 config. If your *.png-file had at least one real transparent pixel, this flag would have been set to true and you wouldn't have to worry about anything.
So when you want to create a scaled Bitmap using
bitmapObject.createScaledBitmap(bitmap, desiredWidth, desiredHeight, false /*filter?*/);
the method checks whether the 'hasAlpha' flag is set to true or false, and in your case it is set to false, which results in obtaining a scaled Bitmap, which was automatically converted to the RGB_565 format.
Therefore on API level >= 12 there is a public method called
public void setHasAlpha (boolean hasAlpha);
which would have solved this issue. So far this was just an explanation of the problem.
I did some research and noticed that the setHasAlpha method has existed for a long time and it's public, but has been hidden (#hide annotation). Here is how it is defined on Android 2.3:
/**
* Tell the bitmap if all of the pixels are known to be opaque (false)
* or if some of the pixels may contain non-opaque alpha values (true).
* Note, for some configs (e.g. RGB_565) this call is ignore, since it does
* not support per-pixel alpha values.
*
* This is meant as a drawing hint, as in some cases a bitmap that is known
* to be opaque can take a faster drawing case than one that may have
* non-opaque per-pixel alpha values.
*
* #hide
*/
public void setHasAlpha(boolean hasAlpha) {
nativeSetHasAlpha(mNativeBitmap, hasAlpha);
}
Now here is my solution proposal. It does not involve any copying of bitmap data:
Checked at runtime using java.lang.Reflect if the current
Bitmap implementation has a public 'setHasAplha' method.
(According to my tests it works perfectly since API level 3, and i haven't tested lower versions, because JNI wouldn't work). You may have problems if a manufacturer has explicitly made it private, protected or deleted it.
Call the 'setHasAlpha' method for a given Bitmap object using JNI.
This works perfectly, even for private methods or fields. It is official that JNI does not check whether you are violating the access control rules or not.
Source: http://java.sun.com/docs/books/jni/html/pitfalls.html (10.9)
This gives us great power, which should be used wisely. I wouldn't try modifying a final field, even if it would work (just to give an example). And please note this is just a workaround...
Here is my implementation of all necessary methods:
JAVA PART:
// NOTE: this cannot be used in switch statements
private static final boolean SETHASALPHA_EXISTS = setHasAlphaExists();
private static boolean setHasAlphaExists() {
// get all puplic Methods of the class Bitmap
java.lang.reflect.Method[] methods = Bitmap.class.getMethods();
// search for a method called 'setHasAlpha'
for(int i=0; i<methods.length; i++) {
if(methods[i].getName().contains("setHasAlpha")) {
Log.i(TAG, "method setHasAlpha was found");
return true;
}
}
Log.i(TAG, "couldn't find method setHasAlpha");
return false;
}
private static void setHasAlpha(Bitmap bitmap, boolean value) {
if(bitmap.hasAlpha() == value) {
Log.i(TAG, "bitmap.hasAlpha() == value -> do nothing");
return;
}
if(!SETHASALPHA_EXISTS) { // if we can't find it then API level MUST be lower than 12
// couldn't find the setHasAlpha-method
// <-- provide alternative here...
return;
}
// using android.os.Build.VERSION.SDK to support API level 3 and above
// use android.os.Build.VERSION.SDK_INT to support API level 4 and above
if(Integer.valueOf(android.os.Build.VERSION.SDK) <= 11) {
Log.i(TAG, "BEFORE: bitmap.hasAlpha() == " + bitmap.hasAlpha());
Log.i(TAG, "trying to set hasAplha to true");
int result = setHasAlphaNative(bitmap, value);
Log.i(TAG, "AFTER: bitmap.hasAlpha() == " + bitmap.hasAlpha());
if(result == -1) {
Log.e(TAG, "Unable to access bitmap."); // usually due to a bug in the own code
return;
}
} else { //API level >= 12
bitmap.setHasAlpha(true);
}
}
/**
* Decodes a Bitmap from the SD card
* and scales it if necessary
*/
public Bitmap decodeBitmapFromFile(String pathToImage, int pixels_limit) {
Bitmap bitmap;
Options opt = new Options();
opt.inDither = false; //important
opt.inPreferredConfig = Bitmap.Config.ARGB_8888;
bitmap = BitmapFactory.decodeFile(pathToImage, opt);
if(bitmap == null) {
Log.e(TAG, "unable to decode bitmap");
return null;
}
setHasAlpha(bitmap, true); // if necessary
int numOfPixels = bitmap.getWidth() * bitmap.getHeight();
if(numOfPixels > pixels_limit) { //image needs to be scaled down
// ensures that the scaled image uses the maximum of the pixel_limit while keeping the original aspect ratio
// i use: private static final int pixels_limit = 1280*960; //1,3 Megapixel
imageScaleFactor = Math.sqrt((double) pixels_limit / (double) numOfPixels);
Bitmap scaledBitmap = Bitmap.createScaledBitmap(bitmap,
(int) (imageScaleFactor * bitmap.getWidth()), (int) (imageScaleFactor * bitmap.getHeight()), false);
bitmap.recycle();
bitmap = scaledBitmap;
Log.i(TAG, "scaled bitmap config: " + bitmap.getConfig().toString());
Log.i(TAG, "pixels_limit = " + pixels_limit);
Log.i(TAG, "scaled_numOfpixels = " + scaledBitmap.getWidth()*scaledBitmap.getHeight());
setHasAlpha(bitmap, true); // if necessary
}
return bitmap;
}
Load your lib and declare the native method:
static {
System.loadLibrary("bitmaputils");
}
private static native int setHasAlphaNative(Bitmap bitmap, boolean value);
Native section ('jni' folder)
Android.mk:
LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_MODULE := bitmaputils
LOCAL_SRC_FILES := bitmap_utils.c
LOCAL_LDLIBS := -llog -ljnigraphics -lz -ldl -lgcc
include $(BUILD_SHARED_LIBRARY)
bitmapUtils.c:
#include <jni.h>
#include <android/bitmap.h>
#include <android/log.h>
#define LOG_TAG "BitmapTest"
#define Log_i(...) __android_log_print(ANDROID_LOG_INFO,LOG_TAG,__VA_ARGS__)
#define Log_e(...) __android_log_print(ANDROID_LOG_ERROR,LOG_TAG,__VA_ARGS__)
// caching class and method IDs for a faster subsequent access
static jclass bitmap_class = 0;
static jmethodID setHasAlphaMethodID = 0;
jint Java_com_example_bitmaptest_MainActivity_setHasAlphaNative(JNIEnv * env, jclass clazz, jobject bitmap, jboolean value) {
AndroidBitmapInfo info;
void* pixels;
if (AndroidBitmap_getInfo(env, bitmap, &info) < 0) {
Log_e("Failed to get Bitmap info");
return -1;
}
if (info.format != ANDROID_BITMAP_FORMAT_RGBA_8888) {
Log_e("Incompatible Bitmap format");
return -1;
}
if (AndroidBitmap_lockPixels(env, bitmap, &pixels) < 0) {
Log_e("Failed to lock the pixels of the Bitmap");
return -1;
}
// get class
if(bitmap_class == NULL) { //initializing jclass
// NOTE: The class Bitmap exists since API level 1, so it just must be found.
bitmap_class = (*env)->GetObjectClass(env, bitmap);
if(bitmap_class == NULL) {
Log_e("bitmap_class == NULL");
return -2;
}
}
// get methodID
if(setHasAlphaMethodID == NULL) { //initializing jmethodID
// NOTE: If this fails, because the method could not be found the App will crash.
// But we only call this part of the code if the method was found using java.lang.Reflect
setHasAlphaMethodID = (*env)->GetMethodID(env, bitmap_class, "setHasAlpha", "(Z)V");
if(setHasAlphaMethodID == NULL) {
Log_e("methodID == NULL");
return -2;
}
}
// call java instance method
(*env)->CallVoidMethod(env, bitmap, setHasAlphaMethodID, value);
// if an exception was thrown we could handle it here
if ((*env)->ExceptionOccurred(env)) {
(*env)->ExceptionDescribe(env);
(*env)->ExceptionClear(env);
Log_e("calling setHasAlpha threw an exception");
return -2;
}
if(AndroidBitmap_unlockPixels(env, bitmap) < 0) {
Log_e("Failed to unlock the pixels of the Bitmap");
return -1;
}
return 0; // success
}
That's it. We are done. I've posted the whole code for copy-and-paste purposes.
The actual code isn't that big, but making all these paranoid error checks makes it a lot bigger. I hope this could be helpful to anyone.