Develop Reference

Convert 8bit Grayscale image byte array to a BufferedImage

I have a byte array containing data of the raw grayscale 8bit image, which I need to convert to a BufferedImage. I've tried doing:
BufferedImage image = ImageIO.read(new ByteArrayInputStream(bytes));
However, the resulting image object is null which means I'm doing something wrong here.
What's the correct way of making such a conversion?

There are two good ways to do this, depending on your use case.
Either create a new, gray image, and copy the data into it. This will keep the image "managed", which may lead to better rendering performance (ie. on screen). But it will need twice as much memory, and copy the data from your input to the image.
The other, is to create the gray image directly "around" your existing pixel data. This will be faster, and use almost no extra heap, as it avoids copying the pixel data. But the image will not be managed (as the backing array is exposed and mutable).
Both options are demonstrated below:
int w = 640;
int h = 480;
byte[] imageBytes = new byte[w * h];
// 1 Keeps the image "managed" at the expense of twice the memory + a large array copy
BufferedImage image = new BufferedImage(w, h, BufferedImage.TYPE_BYTE_GRAY);
image.getRaster().setDataElements(0, 0, w, h, imageBytes);
System.out.println("image: " + image);
// 2 Faster, and uses less memory, but will make the image "unmanaged"
ColorModel cm = new ComponentColorModel(ColorSpace.getInstance(ColorSpace.CS_GRAY), false, false, Transparency.OPAQUE, DataBuffer.TYPE_BYTE);
WritableRaster raster = Raster.createInterleavedRaster(new DataBufferByte(imageBytes, imageBytes.length), w, h, w, 1, new int[]{0}, null);
BufferedImage image2 = new BufferedImage(cm, raster, cm.isAlphaPremultiplied(), null);
System.out.println("image2: " + image2);
If the image data isn't in linear gray color space, one could use an IndexColorModel to map the input into whatever range you want:
// Alternate, using IndexColorModel, if your input isn't in linear gray color space
int[] cmap = new int[256]; // TODO: Add ARGB packed colors here...
IndexColorModel icm = new IndexColorModel(8, 256, cmap, 0, false, -1, DataBuffer.TYPE_BYTE);
// As 1
BufferedImage image3 = new BufferedImage(w, h, BufferedImage.TYPE_BYTE_INDEXED, icm);
image3.getRaster().setDataElements(0, 0, w, h, imageBytes);
System.out.println("image3: " + image3);
// As 2
BufferedImage image4 = new BufferedImage(icm, raster, cm.isAlphaPremultiplied(), null);
System.out.println("image4: " + image4);

I've managed to did the conversion for the 640x480 resolution the following way:
BufferedImage image = new BufferedImage(640,480,BufferedImage.TYPE_BYTE_INDEXED);
int i = 0;
for(int y = 0; y < 480; y++)
{
for(int x = 0; x < 640; x++)
{
int g = imageBytes[i++] & 0xFF;
image.setRGB(x,y,new Color(g,g,g).getRGB());
}
}
EDIT: removed useless code (thanks to Marco13)

Java
BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_BYTE_GRAY);
image.getRaster().setDataElements(0, 0, width, height, array));
Kotlin
val image = BufferedImage(width, height, BufferedImage.TYPE_BYTE_GRAY)
image.raster.setDataElements(0, 0, width, height, byteArray )

How to create an image file with fixed size in Android?

I built a simple app that you can pick a photo of yourself, select a border for it and then save it as image. The way I did this is adding 2 ImageViews on top of each other in a parent view. Then converting this parent view to image and save. However with this way, the resulting image size depends on the device screen size. If the device screen is small, a small final image is generated.
What I want is creating an image file with a size of 500x800 pixels at all times regardless of device. What is the correct way to do this?
The preview on the screen could be small, but when I click save button I need it to be exactly 500x800.

First, convert your image to bitmap by :
Bitmap bitmapImage= BitmapFactory.decodeResource(getResources(), R.drawable.large_icon);
Or, if you have Uri of image then use this to convert it to bitmap:
Bitmap bitmap = BitmapFactory.decodeFile(imageUri.getPath());
Both of this will give you a bitmap of your image.
Now to resize your image use this code:
Bitmap scaledBitmap = Bitmap.createScaledBitmap(bitmap, imageWidth, imageHeight, true);
Then convert it into File.

To Add to Jason Answer, we found the best way to scale the image, is to use this to scale it up or down.
public Bitmap scaleCenterCrop(Bitmap source, int newHeight, int newWidth) {
int sourceWidth = source.getWidth();
int sourceHeight = source.getHeight();
// Compute the scaling factors to fit the new height and width, respectively.
// To cover the final image, the final scaling will be the bigger
// of these two.
float xScale = (float) newWidth / sourceWidth;
float yScale = (float) newHeight / sourceHeight;
float scale = Math.max(xScale, yScale);
// Now get the size of the source bitmap when scaled
float scaledWidth = scale * sourceWidth;
float scaledHeight = scale * sourceHeight;
// Let's find out the upper left coordinates if the scaled bitmap
// should be centered in the new size give by the parameters
float left = (newWidth - scaledWidth) / 2;
float top = (newHeight - scaledHeight) / 2;
// The target rectangle for the new, scaled version of the source bitmap will now
// be
RectF targetRect = new RectF(left, top, left + scaledWidth, top + scaledHeight);
// Finally, we create a new bitmap of the specified size and draw our new,
// scaled bitmap onto it.
Bitmap dest = Bitmap.createBitmap(newWidth, newHeight, source.getConfig());
Canvas canvas = new Canvas(dest);
canvas.drawBitmap(source, null, targetRect, null);
return dest;
}

Please try to below code to save bitmap image as custom height & width, Below is a snippet of code that will allow you to resize a Bitmap.
public Bitmap getResizeBitmap(Bitmap bmp, int newHeight, int newWidth) {
int width = bmp.getWidth();
int height = bmp.getHeight();
float scaleWidth = ((float) newWidth) / width;
float scaleHeight = ((float) newHeight) / height;
// CREATE A MATRIX FOR THE MANIPULATION
Matrix matrix = new Matrix();
// RESIZE THE BIT MAP
matrix.postScale(scaleWidth, scaleHeight);
// RECREATE THE NEW BITMAP
Bitmap resizeBitmap = Bitmap.createBitmap(bmp, 0, 0, width, height, matrix, false);
return resizeBitmap;
}

Android Bitmap - Crop a circle into semicircle

I'm trying to cut a circle into semicircles using android canvas. The circle is loaded using Bitmap class.
Here's the example:
I've been looking for any solution, especially the ones which enable you to crop a bitmap using coordinates, but to no avail.
Any help is appreciated, thanks before..

I had the same challenge before and I solved it in a simple way, The main idea is simple! Use a Bitmap mask, Fill the pixel you want to save (in this case a pie) with the highest integer value (0xFFFFFFFF), So you can use a bitwiseAND to gain the result color, Other pixels of the mask Bitmap will be a transparent black color (0x00000000), When you're done with the mask, Create the result Bitmap and fill the pixels as the method below does:
public Bitmap applyPieMask(Bitmap src, float startAngle, float sweepAngle) {
int width = src.getWidth();
int height = src.getHeight();
//create bitmap mask with the same dimension of the src bitmap
Bitmap mask = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
Canvas canvas = new Canvas(mask);
canvas.drawColor(0x00000000);//fill mask bitmap with transparent black!
//init mask paint
Paint maskPaint = new Paint();
maskPaint.setColor(0xFFFFFFFF);//pick highest value for bitwise AND operation
maskPaint.setAntiAlias(true);
//choose entire bitmap as a rect
RectF rect = new RectF(0, 0, width, height);
canvas.drawArc(rect, startAngle, sweepAngle, true, maskPaint);//mask the pie
Bitmap result = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
for (int i = 0; i < height; i++) {
for (int j = 0; j < width; j++) {
//combine src color and mask to gain the result color
int color = mask.getPixel(i, j) & src.getPixel(i, j);
result.setPixel(i, j, color);
}
}
return result;
}
And here we go ...
public void doIt(View view) {
ImageView imageView = (ImageView) findViewById(R.id.iv);
Bitmap src = Bitmap.createBitmap(500, 500, Bitmap.Config.ARGB_8888);
Canvas canvas = new Canvas(src);
canvas.drawColor(Color.BLUE);//fill src bitmap with blue color
imageView.setImageBitmap(applyPieMask(src, -90, 60));
}
Hope you find it helpful

Int Pixel Array To Image

I am trying to take an int array of pixels from a Bitmap on Android and use the int array to make a buffered image. But I'm having some problems. I am able to get the bitmap from android with no problem:
Bitmap b = BitmapFactory.decodeByteArray(data, 0, data.length);
b = Bitmap.createScaledBitmap(b, (int)(b.getWidth() * .3125), (int)(b.getHeight() * .44444444444), false);
int[] arr = new int[b.getHeight() * b.getWidth()];
b.getPixels(arr, 0, b.getWidth(), 0, 0, b.getWidth(), b.getHeight());
I scale the bitmap down and then get the pixels and put them into the int array. Then I send them over a network to the PC where I try to recreate it to a BufferedImage (networking isn't important). Here is the code I use to convert the pixel array to a BufferedImage.
int width = 600;
int height = 479;
BufferedImage bi = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
bi.setRGB(0, 0, width, height, arr, 0, width);
g2d.drawImage(bi, 10, 50, null);
The variable "arr" is the byte array of pixels. Converting to a BufferedImage gives no error and shows the following image:
Obviously this isn't the picture I am trying to get. When I print out 5 of the pixels in the array (just for testing) I get the following and this is the format of the pixels:
-15528956
-15200766
-13558523
-11718123
-12243954
-13294582

Trying to mirror a picture with java android canvas.drawImage

I'm having problems while trying to rotate a picture with java android canvas.drawImage. I'm doing a little game, and I'm painting different pictures on the screen using my drawImage function. However now I want to rotate some little images, I have created a function called drawMirroredImage for this. However now this little images don't appear on the same place.
Here is my code:
public void drawImage(Image Image, int x, int y) {
canvas.drawBitmap(((AndroidImage) Image).bitmap, x, y, null);
}
public void drawMirroredImage(Image Image, int x, int y) {
canvas.save();
canvas.scale(-1.0f, 1.0f);
canvas.drawBitmap(((AndroidImage) Image).bitmap, x - canvas.getWidth(), y, null);
canvas.restore();
}
Anyone knows what I'm doing wrong?
Lot of thanks for helping

Following will work for you.
I found it somewhere on SO itself but don't remember where.
public static Bitmap getReflectionedBitmap(Context context,int resourceId,Bitmap originalImage,int reflectionGap) {
if(originalImage==null)
originalImage = BitmapFactory.decodeResource(context.getResources(),resourceId);
int width = originalImage.getWidth();
int height = originalImage.getHeight();
// This will not scale but will flip on the Y axis
Matrix matrix = new Matrix();
matrix.preScale(1, -1);
// Create a Bitmap with the flip matix applied to it.
// We only want the bottom half of the image
Bitmap reflectionImage = Bitmap.createBitmap(originalImage, 0,
height / 2, width, height / 2, matrix, false);
// Create a new bitmap with same width but taller to fit reflection
Bitmap bitmapWithReflection = Bitmap.createBitmap(width,
(height + height / 2), Config.ARGB_8888);
// Create a new Canvas with the bitmap that's big enough for
// the image plus gap plus reflection
Canvas canvas = new Canvas(bitmapWithReflection);
// Draw in the original image
canvas.drawBitmap(originalImage, 0, 0, null);
// Draw in the gap
Paint deafaultPaint = new Paint();
deafaultPaint.setColor(0xffffffff);
canvas.drawRect(0, height, width, height + reflectionGap , deafaultPaint);
canvas.drawBitmap(reflectionImage, 0, height + reflectionGap, null);
Paint paint = new Paint();
LinearGradient shader = new LinearGradient(0,
originalImage.getHeight(), 0, bitmapWithReflection.getHeight()
+ reflectionGap, 0x70ffffff, 0x00ffffff, TileMode.CLAMP);
// Set the paint to use this shader (linear gradient)
paint.setShader(shader);
// Set the Transfer mode to be porter duff and destination in
paint.setXfermode(new PorterDuffXfermode(Mode.DST_IN));
canvas.drawRect(0, height, width, bitmapWithReflection.getHeight()
+ reflectionGap, paint);
return bitmapWithReflection;
}
I tweaked the snippet a little bit to use it with resource images as well.
Pass in null as parameter in place of Bitmap if you want to create reflection for images in resource.