Android Bitmap Tutorial and Examples.
import android.graphics.Bitmap;
import android.graphics.Matrix;
import android.util.Base64;
import android.util.Log;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
public class ImageUtils {
private static final String TAG = "ImageUtils";
public static byte[] bitmap2Bytes(Bitmap bitmap, int quality, Bitmap.CompressFormat format){
if (bitmap == null){
return null;
}else {
ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
bitmap.compress(format,quality,outputStream);
try {
outputStream.flush();
outputStream.close();
} catch (IOException e) {
e.printStackTrace();
}
return outputStream.toByteArray();
}
}
public static String bitmap2Base64(Bitmap bitmap, int quality, Bitmap.CompressFormat format){
byte[] bytes = bitmap2Bytes(bitmap,quality,format);
return Base64.encodeToString(bytes,Base64.DEFAULT)
.replace("n","")
.replace("r","")
.replace("t","");
}
public static Bitmap scaleBitmap(Bitmap srcBitmap, int maxWidth, int maxHeight){
int width = srcBitmap.getWidth();
int height = srcBitmap.getHeight();
Log.d(TAG, "scaleBitmap: nwidth = " + width + "nheight = " + height);
int desiredWidth = Math.min(width,maxWidth);
int desiredHeight = Math.min(height,maxHeight);
float scaleWidth = ((float) desiredWidth / width);
float scaleHeight = ((float) desiredHeight / height);
float scaled = Math.min(scaleHeight,scaleWidth);
Matrix matrix = new Matrix();
matrix.postScale(scaled,scaled);
return Bitmap.createBitmap(srcBitmap,0,0,width,height,matrix,true);
}
public static Bitmap convert2Gray(Bitmap bitmap) {
int width = bitmap.getWidth();
int height = bitmap.getHeight();
int[] pixs = new int[width * height];
bitmap.getPixels(pixs, 0, width, 0, 0, width, height);
int alpha = 0xFF << 24;
for (int i = 0; i < height; i++) {
for (int j = 0; j < width; j++) {
int color = pixs[width * i + j];
int red = (color & 0x00FF0000) >> 16;
int green = (color & 0x0000FF00) >> 8;
int blue = (color & 0x000000FF);
color = (red + green + blue) / 3;
color = alpha | (color << 16) | (color << 8)| color;
pixs[width * i + j] = color;
}
}
Bitmap result = Bitmap.createBitmap(width,height, Bitmap.Config.RGB_565);
result.setPixels(pixs,0,width,0,0,width,height);
return result;
}
}
1. Download Bitmap From the Web
Let’s see how we can download bitmap from the internet via HttpURLConnection class.
private Bitmap downloadUrl(String myurl) throws IOException {
try {
URL url = new URL(myurl);
HttpURLConnection connection = (HttpURLConnection) url
.openConnection();
connection.setDoInput(true);
connection.connect();
InputStream input = connection.getInputStream();
Bitmap myBitmap = BitmapFactory.decodeStream(input);
return myBitmap;
} catch (IOException e) {
return null;
}
}
Here’s the full example with AsyncTask:
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.AsyncTask;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;
public class HttpImageGetTask extends AsyncTask<String, Void, Bitmap> {
private OnImageDownloadCompleted listener;
public HttpImageGetTask(OnImageDownloadCompleted listener) {
this.listener = listener;
}
@Override
protected Bitmap doInBackground(String... urls) {
try {
return downloadUrl(urls[0]);
} catch (IOException e) {
return null;
}
}
@Override
protected void onPostExecute(Bitmap result) {
listener.onBitmapCompleted(result);
}
private Bitmap downloadUrl(String myurl) throws IOException {
try {
URL url = new URL(myurl);
HttpURLConnection connection = (HttpURLConnection) url
.openConnection();
connection.setDoInput(true);
connection.connect();
InputStream input = connection.getInputStream();
Bitmap myBitmap = BitmapFactory.decodeStream(input);
return myBitmap;
} catch (IOException e) {
return null;
}
}
}
2. How to Get MD5 of a String
This is a helper method we will use in some of the following examples.
public static String getMD5(String content) {
try {
MessageDigest digest = MessageDigest.getInstance("MD5");
digest.update(content.getBytes());
return getHashString(digest);
} catch (Exception e) {
}
return null;
}
3. How to Load Bitmap into ImageView From File System
You cam also load a Bitmap from the file system. You need however to pass the image path instead of url.
public static Bitmap getBitmap2(String imagePath) {
if (!(imagePath.length() > 5)) {
return null;
}
File cache_file = new File(new File(
Environment.getExternalStorageDirectory(), "xxxx"),
"cachebitmap");
cache_file = new File(cache_file, getMD5(imagePath));
if (cache_file.exists()) {
return BitmapFactory.decodeFile(getBitmapCache(imagePath));
} else {
try {
URL url = new URL(imagePath);
HttpURLConnection conn = (HttpURLConnection) url
.openConnection();
conn.setConnectTimeout(5000);
if (conn.getResponseCode() == 200) {
InputStream inStream = conn.getInputStream();
File file = new File(new File(
Environment.getExternalStorageDirectory(), "xxxx"),
"cachebitmap");
if (!file.exists()) {
file.mkdirs();
}
file = new File(file, getMD5(imagePath));
FileOutputStream out = new FileOutputStream(file);
byte buff[] = new byte[1024];
int len = 0;
while ((len = inStream.read(buff)) != -1) {
out.write(buff, 0, len);
}
out.close();
inStream.close();
return BitmapFactory.decodeFile(getBitmapCache(imagePath));
}
} catch (Exception e) {
}
}
return null;
}
4. How to Get Bitmap Cache
public static String getBitmapCache(String url) {
File file = new File(new File(
Environment.getExternalStorageDirectory(), "xxxx"),
"cachebitmap");
file = new File(file, getMD5(url));
if (file.exists()) {
return file.getAbsolutePath();
}
return null;
}
5. How to Load Bitmap into ImageView via Glide
public static void displayImageBitmap(String url,ImageView imageView) {
Glide.with(MainApp.getContext())
.load(url)
.asBitmap()
.thumbnail(0.2f)
.placeholder(R.drawable.pictures_no)
.diskCacheStrategy(DiskCacheStrategy.SOURCE)
.into(imageView);
}
6. How to Get a Hash string of a MessageDigest
private static String getHashString(MessageDigest digest) {
StringBuilder builder = new StringBuilder();
for (byte b : digest.digest()) {
builder.append(Integer.toHexString((b >> 4) & 0xf));
builder.append(Integer.toHexString(b & 0xf));
}
return builder.toString().toLowerCase();
}
7. How to Save a Bitmap to Local File
You pass the File object onto which we wish to save our Bitmap. The Bitmap also is passed as a parameter to our method.
public static String saveBitmapToLocal(File file , Bitmap bitmap) {
try {
if(!file.exists()) {
file.createNewFile();
}
BufferedOutputStream bufferedOutputStream = new BufferedOutputStream(new FileOutputStream(file));
bitmap.compress(Bitmap.CompressFormat.PNG, 100, bufferedOutputStream);
bufferedOutputStream.close();
LogUtil.d(TAG, "photo image from data, path:" + file.getAbsolutePath());
return file.getAbsolutePath();
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
8. How to Extract Thumbnail From Image
Then we return a Bitmap. The path to the image is provided to us alongside the dimensions of the thumbanial as well as whether to crop the image.
@TargetApi(Build.VERSION_CODES.HONEYCOMB)
public static Bitmap extractThumbNail(final String path, final int width, final int height, final boolean crop) {
Assert.assertTrue(path != null && !path.equals("") && height > 0 && width > 0);
BitmapFactory.Options options = new BitmapFactory.Options();
try {
options.inJustDecodeBounds = true;
Bitmap tmp = BitmapFactory.decodeFile(path);
if (tmp != null) {
tmp.recycle();
tmp = null;
}
LogUtil.d(TAG, "extractThumbNail: round=" + width + "x" + height + ", crop=" + crop);
final double beY = options.outHeight * 1.0 / height;
final double beX = options.outWidth * 1.0 / width;
LogUtil.d(TAG, "extractThumbNail: extract beX = " + beX + ", beY = " + beY);
options.inSampleSize = (int) (crop ? (beY > beX ? beX : beY) : (beY < beX ? beX : beY));
if (options.inSampleSize <= 1) {
options.inSampleSize = 1;
}
// NOTE: out of memory error
while (options.outHeight * options.outWidth / options.inSampleSize > MAX_DECODE_PICTURE_SIZE) {
options.inSampleSize++;
}
int newHeight = height;
int newWidth = width;
if (crop) {
if (beY > beX) {
newHeight = (int) (newWidth * 1.0 * options.outHeight / options.outWidth);
} else {
newWidth = (int) (newHeight * 1.0 * options.outWidth / options.outHeight);
}
} else {
if (beY < beX) {
newHeight = (int) (newWidth * 1.0 * options.outHeight / options.outWidth);
} else {
newWidth = (int) (newHeight * 1.0 * options.outWidth / options.outHeight);
}
}
options.inJustDecodeBounds = false;
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.ICE_CREAM_SANDWICH) {
options.inMutable = true;
}
LogUtil.i(TAG, "bitmap required size=" + newWidth + "x" + newHeight + ", orig=" + options.outWidth + "x" + options.outHeight + ", sample=" + options.inSampleSize);
Bitmap bm = BitmapFactory.decodeFile(path);
setInNativeAlloc(options);
if (bm == null) {
Log.e(TAG, "bitmap decode failed");
return null;
}
LogUtil.i(TAG, "bitmap decoded size=" + bm.getWidth() + "x" + bm.getHeight());
final Bitmap scale = Bitmap.createScaledBitmap(bm, newWidth, newHeight, true);
if (scale != null) {
bm.recycle();
bm = scale;
}
if (crop) {
final Bitmap cropped = Bitmap.createBitmap(bm, (bm.getWidth() - width) >> 1, (bm.getHeight() - height) >> 1, width, height);
if (cropped == null) {
return bm;
}
bm.recycle();
bm = cropped;
LogUtil.i(TAG, "bitmap croped size=" + bm.getWidth() + "x" + bm.getHeight());
}
return bm;
} catch (final OutOfMemoryError e) {
LogUtil.e(TAG, "decode bitmap failed: " + e.getMessage());
options = null;
}
return null;
}
9. How to Decode a Stream into Bitmap
public static Bitmap decodeStream(InputStream stream , float dip) {
BitmapFactory.Options options = new BitmapFactory.Options();
if(dip != 0.0F) {
options.inDensity = (int)(160.0F * dip);
}
options.inPreferredConfig = Bitmap.Config.ARGB_8888;
setInNativeAlloc(options);
try {
Bitmap bitmap = BitmapFactory.decodeStream(stream, null,options);
return bitmap;
} catch (OutOfMemoryError e) {
options.inPreferredConfig = Bitmap.Config.RGB_565;
setInNativeAlloc(options);
try {
Bitmap bitmap = BitmapFactory.decodeStream(stream, null,options);
return bitmap;
} catch (OutOfMemoryError e2) {
}
}
return null;
}
10. How to Create a new Bitmap
public static Bitmap newBitmap(int width, int height,Bitmap.Config config) {
try {
Bitmap bitmap = Bitmap.createBitmap(width, height,config);
return bitmap;
} catch (Throwable localThrowable) {
LogUtil.e(TAG, localThrowable.getMessage());
}
return null;
}
11. How to Convert a Bitmap to an Array
You pass the Bitmap as a parameter and we compress it and convert it to a byte array.
public static byte[] bmpToByteArray(final Bitmap bmp, final boolean needRecycle) {
ByteArrayOutputStream output = new ByteArrayOutputStream();
bmp.compress(Bitmap.CompressFormat.PNG, 100, output);
if (needRecycle) {
bmp.recycle();
}
byte[] result = output.toByteArray();
try {
output.close();
} catch (Exception e) {
e.printStackTrace();
}
return result;
}
12. How to load a Bitmap From a File name
Here’s an even simpler example of loading a bitmap from a file name and returning it.
public static Bitmap loadFromFile(String filename) {
try {
File f = new File(filename);
if (!f.exists()) {
return null;
}
Bitmap tmp = BitmapFactory.decodeFile(filename);
// tmp = setExifInfo(filename, tmp);
return tmp;
} catch (Exception e) {
return null;
}
}
13. How to Compress an Image
We will compress the image and return it as a Bitmap. Basically you pass us a bitmap and we compress it and return it to you.
public Bitmap compressImage(Bitmap image) {
ByteArrayOutputStream baos = new ByteArrayOutputStream();
image.compress(Bitmap.CompressFormat.JPEG, 100, baos);
int options = 100;
while (baos.toByteArray().length / 1024 > 128) {
baos.reset();
image.compress(Bitmap.CompressFormat.JPEG,options, baos);/
options -= 10;
}
ByteArrayInputStream isBm = new ByteArrayInputStream(baos.toByteArray());
Bitmap bitmap = BitmapFactory.decodeStream(isBm, null, null);
// bitmap.
return bitmap;
}
14. How to load a Bitmap From a Path
Just pass us the image path then we will decode that file using the BitmapFactory‘s decodeFile method.
public static Bitmap loadBitmap(String imgpath) {
return BitmapFactory.decodeFile(imgpath);
}
15. How to Scale a Bitmap
Pass us the Bitmap, it’s width and height then we scale it.
private static Bitmap scaleBitmap(Bitmap bitmap, float ww, float hh) {
double scaleWidth = 1;
double scaleHeight = 1;
int widthOri = bitmap.getWidth();
int heightOri = bitmap.getHeight();
if (widthOri > heightOri && widthOri > ww) {
scaleWidth = 1.0 / (double) (widthOri / ww);
scaleHeight = scaleWidth;
} else if (widthOri < heightOri && heightOri > hh) {
scaleHeight = 1.0 / (double) (heightOri / hh);
scaleWidth = scaleHeight;
}
Matrix matrix = new Matrix();
matrix.postScale((float) scaleWidth, (float) scaleHeight);
Bitmap resizedBitmap = Bitmap.createBitmap(bitmap, 0, 0,
bitmap.getWidth(), bitmap.getHeight(), matrix, true);
16. How to Capture Screenshot and Return it as a Byte
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.view.View;
public class ScreenShotUtil {
public static Bitmap capture(View view, float width, float height, boolean scroll, Bitmap.Config config) {
if (!view.isDrawingCacheEnabled()) {
view.setDrawingCacheEnabled(true);
}
if(width==0){
width= MainApp.getInstance().getScreenWidth();
}
if(height==0){
height= MainApp.getInstance().getScreenHeight();
}
Bitmap bitmap = Bitmap.createBitmap((int) width, (int) height, config);
bitmap.eraseColor(Color.WHITE);
Canvas canvas = new Canvas(bitmap);
int left = view.getLeft();
int top = view.getTop();
if (scroll) {
left = view.getScrollX();
top = view.getScrollY();
}
int status = canvas.save();
canvas.translate(-left, -top);
float scale = width / view.getWidth();
canvas.scale(scale, scale, left, top);
view.draw(canvas);
canvas.restoreToCount(status);
Paint alphaPaint = new Paint();
alphaPaint.setColor(Color.TRANSPARENT);
canvas.drawRect(0f, 0f, 1f, height, alphaPaint);
canvas.drawRect(width - 1f, 0f, width, height, alphaPaint);
canvas.drawRect(0f, 0f, width, 1f, alphaPaint);
canvas.drawRect(0f, height - 1f, width, height, alphaPaint);
canvas.setBitmap(null);
return bitmap;
}
}
17. How to Convert Bitmap to Base64 String
public static String convertBitmapToString(Bitmap bitmap) {
ByteArrayOutputStream baos = new ByteArrayOutputStream();// outputstream
bitmap.compress(Bitmap.CompressFormat.PNG, 100, baos);
byte[] b = baos.toByteArray();
return Base64.encodeToString(b, Base64.DEFAULT);
}
18. How to Convert String to Bitmap
public static Bitmap convertStringToBitmap(String st) {
// OutputStream out;
Bitmap bitmap = null;
try
{
// out = new FileOutputStream("/sdcard/aa.jpg");
byte[] bitmapArray;
bitmapArray = Base64.decode(st, Base64.DEFAULT);
bitmap = BitmapFactory.decodeByteArray(bitmapArray, 0, bitmapArray.length);
// bitmap.compress(Bitmap.CompressFormat.PNG, 100, out);
return bitmap;
}
catch (Exception e)
{
return null;
}
19. How to Create a bitmap from the supplied view.
You supply the View from which you want us to create the bitmap.
public static Bitmap createBitmapFromView(View view) {
final Bitmap bitmap = Bitmap.createBitmap(view.getWidth(), view.getHeight(), Bitmap.Config.ARGB_8888);
final Canvas canvas = new Canvas(bitmap);
view.layout(view.getLeft(), view.getTop(), view.getRight(), view.getBottom());
view.draw(canvas);
return bitmap;
}
