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Manipulating the Alpha value of BufferedImage

In the code i'm setting the alpha value of a pixel to 100 for entire image and I want the Alpha value to be 100 while reading the image. But at the retrieving part it gives me 255(Default Value) . What is wrong ? and how to solve it ? Any Help would be appreciated...
class Demo
{
Demo()
{
try
{
BufferedImage im2 = new BufferedImage(width,height,BufferedImage.TYPE_INT_ARGB);
File f2 = new File("test2.jpg");
im2 = ImageIO.read(f2);
int width1 = im2.getWidth();
int height1 = im2.getHeight();
for(int i=0;i<height1;i++)
{
for(int j=0;j<width1;j++)
{
Color c = new Color(50,0,0,100); //Set the alpha value to 100
im2.setRGB(j,i,c.getRGB()); // for every pixel
}
}
File f = new File("Demo_copy.jpg");
ImageIO.write(im2,"jpg",f);
// Retrieving.........
BufferedImage im1;
File f1 = new File("Demo_copy.jpg");
im1 = ImageIO.read(f1);
int width = im1.getWidth();
int height = im1.getHeight();
for(int i=0;i<height;i++)
{
for(int j=0;j<width;j++)
{
int pixel = im1.getRGB(j,i);
Color c = new Color(pixel,true);
int a = c.getAlpha();
System.out.println("Alpha value is :"+a); // Printing Alpha : 255 for every pixel
}
}
}catch(Exception e){}
}
public static void main(String [] ar)
{
new Demo();
}
}

The new BufferedImage(...) you assign to im2 is just thrown away (garbage collected) after you assign a new value from ImageIO.read(..). As the new value is a JPEG and doesn't have alpha, it does not matter what alpha values you set. They will always stay 255 (completely opaque).
Instead, you probably want to do something like this:
// Read opaque image...
BufferedImage img = ImageIO.read(new File("test2.jpg"));
// ...convert image to TYPE_INT_ARGB...
BufferedImage im2 = new BufferedImage(img.getWidth(), img.getHeight(), BufferedImage.TYPE_INT_ARGB);
Graphics2D g = im2.createGraphics();
try {
g.drawImage(img, 0, 0, null);
}
finally {
g.dispose();
}
// ... loop over and change alpha in im2 as before
Finally, you should write the image in a format that supports lossless alpha, like PNG instead of JPEG, to be sure you get the values you expect:
ImageIO.write(im2,"PNG", new File("Demo_copy.png"));
PS: It might just work using JPEG too, as the built-in Java ImageIO JPEG plugin supports reading/writing JPEGs with alpha values. However, most other software will misinterpret these as CMYK JPEGs, and the colors will look all wrong. Also, JPEG is lossy, so you will most likely not see the exact alpha value (100) as you would expect on the receiving end. That's why I suggest using PNG. TIFF or other format that supports alpha would also work, but requires extra plugins.

Java SWT: Displaying image Pixel by Pixel but Blues look Yellow

I am displaying an image Pixel by Pixel. All the blues look yellow. I suspect the issue is with the PalletteData or with the following line(The Pixel object just holds the int representation of the colour):
p = (pixel.Alpha<<24) | (pixel.Red<<16) | (pixel.Green<<8) | pixel.Blue;
Note: as the call is from Java to C++ accross JNI, there are some conversions:
Each colour is read in to an unsigned char. Then it is converted to char to pass accross JNI. Then is read as a byte on the Java side. Then converted to Int
Here is the full listing. Can you see what my problem is?
PaletteData palette=new PaletteData(0xff0000,0x00ff00,0xff);
ImageData imageData = new ImageData(width, height,32,palette);
int pixelVecLoc=0;
for (int h = 0; h<1300; h++)
{
for (int w = 0; w<1300; w++)
{
int p = 0;
Pixel pixel = pixelVec.get(pixelVecLoc);
p = (pixel.Alpha<<24) | (pixel.Red<<16) | (pixel.Green<<8) | pixel.Blue;
imageData.setPixel(w, h, p);
pixelVecLoc++;
}
}
imageData = imageData.scaledTo(600, 500);
Image image = ImageDescriptor.createFromImageData(imageData).createImage();
//Image image = new GVImageProcessingJNIWrapper().GetBMPFromGTX();
e.gc.drawImage(image, 0, 0);

I figured it out!!! It was the conversion from byte to int.
I needed to use this:
Byte.toUnsignedInt

Converting byte array to png

I have a byte array obtained from an image using the following code.
String path = "/home/mypc/Desktop/Steganography/image.png";
File file = new File(path);
BufferedImage bfimage = ImageIO.read(file);
ByteArrayOutputStream baos = new ByteArrayOutputStream();
ImageIO.write(bfimage, "png", baos);
baos.flush();
byte[] img_in_bytes = baos.toByteArray();
baos.close();
Then I converted these bytes back to png image using the following code.
BufferedImage final_img = ImageIO.read(new ByteArrayInputStream(img_in_bytes));
File output_file = new File("Stegano2.png");
ImageIO.write(final_img, "png", output_file);
It is perfectly fine if i just execute this piece of code. But if i try to modify some of the bytes in between, say like this :
Insert_number_to_image(image_in_bytes, 10);
and my method "Inset_number_to_image" goes like this :
static void Insert_number_to_image(byte[] image, int size){
byte[] size_in_byte = new byte[4];
size_in_byte[0] = (byte)(size >>> 0);
size_in_byte[1] = (byte)(size >>> 8);
size_in_byte[2] = (byte)(size >>> 16);
size_in_byte[3] = (byte)(size >>> 24);
byte temp;
int count = 0;
for(int i=0; i<4; i++)
{
for(int j=0; j<8; j++)
{
temp = size_in_byte[i];
temp = (byte)(temp >>> j);
temp = (byte)(temp & 1);
if(temp == 1)
{
image[count] = (byte)(image[count] | 1);
}
else if(temp == 0)
{
image[count] = (byte)(image[count] & (byte)(~(1)));
}
count++;
}
}
}
then after that, when i save the modified byte array as png image using same code mentioned above, i am getting this error :
Exception in thread "main" java.lang.IllegalArgumentException: image == null!
at javax.imageio.ImageTypeSpecifier.createFromRenderedImage(ImageTypeSpecifier.java:925)
at javax.imageio.ImageIO.getWriter(ImageIO.java:1591)
at javax.imageio.ImageIO.write(ImageIO.java:1520)
at Steganography.main(Steganography.java:211)

What you're using is the raw bytestream of a PNG image. PNG is a compressed format, where the bytestream doesn't reflect any of the pixel values directly and even changing one byte might irreversibly corrupt the file.
What you want instead is to extract the pixel data to a byte array with
byte[] pixels = ((DataBufferByte) img.getRaster().getDataBuffer()).getData();
Now you can modify the pixel values however you want. When you are ready to save that back to a file, convert the pixel byte array to a BufferedImage by putting your pixel array in a DataBufferByte object and passing that to a WriteableRaster, which you then use to create a BufferedImage.
Your method would work for formats where the raw bytestream does directly represent the pixels, such as in BMP. However, even then you'd have to skip the first few bytes to avoid corrupting the header.

How can I print an image on a Bluetooth printer in Android?

I have to print some data on thermal bluetooth printer, I'm doing with this:
String message="abcdef any message 12345";
byte[] send;
send = message.getBytes();
mService.write(send);
It works well for text, but not for images. I think I need to get the byte[] of the image data. I tried getting the data of the image this way:
Bitmap bitmap=BitmapFactory.decodeResource(getResources(), R.drawable.qrcode);
ByteArrayOutputStream stream=new ByteArrayOutputStream();
bitmap.compress(Bitmap.CompressFormat.PNG, 90, stream);
byte[] image=stream.toByteArray();
Unfortunately the printer prints a lot of strange characters (approx. 50 cm of paper). I don't know how to print the image.
I would like to try getting the pixels of the bitmap and next converting it to a byte[] and sending it, but i don't know how to do it.
Thanks
UPDATE:
After so much time, i'm doing this: I have a method called print_image(String file), the which gets the path of the image that i want to print:
private void print_image(String file) {
File fl = new File(file);
if (fl.exists()) {
Bitmap bmp = BitmapFactory.decodeFile(file);
convertBitmap(bmp);
mService.write(PrinterCommands.SET_LINE_SPACING_24);
int offset = 0;
while (offset < bmp.getHeight()) {
mService.write(PrinterCommands.SELECT_BIT_IMAGE_MODE);
for (int x = 0; x < bmp.getWidth(); ++x) {
for (int k = 0; k < 3; ++k) {
byte slice = 0;
for (int b = 0; b < 8; ++b) {
int y = (((offset / 8) + k) * 8) + b;
int i = (y * bmp.getWidth()) + x;
boolean v = false;
if (i < dots.length()) {
v = dots.get(i);
}
slice |= (byte) ((v ? 1 : 0) << (7 - b));
}
mService.write(slice);
}
}
offset += 24;
mService.write(PrinterCommands.FEED_LINE);
mService.write(PrinterCommands.FEED_LINE);
mService.write(PrinterCommands.FEED_LINE);
mService.write(PrinterCommands.FEED_LINE);
mService.write(PrinterCommands.FEED_LINE);
mService.write(PrinterCommands.FEED_LINE);
}
mService.write(PrinterCommands.SET_LINE_SPACING_30);
} else {
Toast.makeText(this, "file doesn't exists", Toast.LENGTH_SHORT)
.show();
}
}
I did it based on this post
This is the class PrinterCommands:
public class PrinterCommands {
public static final byte[] INIT = {27, 64};
public static byte[] FEED_LINE = {10};
public static byte[] SELECT_FONT_A = {27, 33, 0};
public static byte[] SET_BAR_CODE_HEIGHT = {29, 104, 100};
public static byte[] PRINT_BAR_CODE_1 = {29, 107, 2};
public static byte[] SEND_NULL_BYTE = {0x00};
public static byte[] SELECT_PRINT_SHEET = {0x1B, 0x63, 0x30, 0x02};
public static byte[] FEED_PAPER_AND_CUT = {0x1D, 0x56, 66, 0x00};
public static byte[] SELECT_CYRILLIC_CHARACTER_CODE_TABLE = {0x1B, 0x74, 0x11};
public static byte[] SELECT_BIT_IMAGE_MODE = {0x1B, 0x2A, 33, -128, 0};
public static byte[] SET_LINE_SPACING_24 = {0x1B, 0x33, 24};
public static byte[] SET_LINE_SPACING_30 = {0x1B, 0x33, 30};
public static byte[] TRANSMIT_DLE_PRINTER_STATUS = {0x10, 0x04, 0x01};
public static byte[] TRANSMIT_DLE_OFFLINE_PRINTER_STATUS = {0x10, 0x04, 0x02};
public static byte[] TRANSMIT_DLE_ERROR_STATUS = {0x10, 0x04, 0x03};
public static byte[] TRANSMIT_DLE_ROLL_PAPER_SENSOR_STATUS = {0x10, 0x04, 0x04};
}
As is seen in the print_image method I'm calling a method, called convertBitmap, and im sending a bitmap, this is the code:
public String convertBitmap(Bitmap inputBitmap) {
mWidth = inputBitmap.getWidth();
mHeight = inputBitmap.getHeight();
convertArgbToGrayscale(inputBitmap, mWidth, mHeight);
mStatus = "ok";
return mStatus;
}
private void convertArgbToGrayscale(Bitmap bmpOriginal, int width,
int height) {
int pixel;
int k = 0;
int B = 0, G = 0, R = 0;
dots = new BitSet();
try {
for (int x = 0; x < height; x++) {
for (int y = 0; y < width; y++) {
// get one pixel color
pixel = bmpOriginal.getPixel(y, x);
// retrieve color of all channels
R = Color.red(pixel);
G = Color.green(pixel);
B = Color.blue(pixel);
// take conversion up to one single value by calculating
// pixel intensity.
R = G = B = (int) (0.299 * R + 0.587 * G + 0.114 * B);
// set bit into bitset, by calculating the pixel's luma
if (R < 55) {
dots.set(k);//this is the bitset that i'm printing
}
k++;
}
}
} catch (Exception e) {
// TODO: handle exception
Log.e(TAG, e.toString());
}
}
This is the printer that i'm using, resolution: 8 dots/mm, 576 dots/line
And this is what I like to do (i did it with the same printer, but with an app downloaded from play store)
This is what i'm getting now
Closer:
Closer2:
A little part of the image can be seen, so I think that i'm closer to can print the image...
The image that i'm using is this (576x95):
And this is the converted image (i'm converting it with the upper code):
So, the answer is: what I'm doing wrong?, I think that the error is in this command:
public static byte[] SELECT_BIT_IMAGE_MODE = {0x1B, 0x2A, 33, -128, 0};
But, how can I calculate the correct values for my image?, thanks

I solve it converting Bitmap to Byte array. Remember that your image must be black & white format.
For full source code:
https://github.com/imrankst1221/Thermal-Printer-in-Android
public void printPhoto() {
try {
Bitmap bmp = BitmapFactory.decodeResource(getResources(),
R.drawable.img);
if(bmp!=null){
byte[] command = Utils.decodeBitmap(bmp);
printText(command);
}else{
Log.e("Print Photo error", "the file isn't exists");
}
} catch (Exception e) {
e.printStackTrace();
Log.e("PrintTools", "the file isn't exists");
}
}

I also tried this and I got to my own solution and I think I figured out how the SELECT_BIT_IMAGE_MODE command works.
The command public static byte[] SELECT_BIT_IMAGE_MODE = {0x1B, 0x2A, 33, 255, 3}; in the class PrinterCommands is the POS Command for image printing.
The first two are pretty standard, the next three determine the mode and the dimensions of the image to be printed. For the sake of this solution, let's just assume that the second element (33, we are indexed zero) is always 33.
The last two elements of that byte[] refers to the Width (in pixels) property of the image that you want to print, element 3 is sometimes referred to as nL and element 4 is sometimes referred to as nH. They are actually both referring to the Width, nL is the Low Byte while nH is the High Byte. This means that we can have at the most an image with a width of 1111 1111 1111 1111b (binary) which is 65535d (decimal), though I haven't tried it yet. If nL or nH aren't set to the proper values, then there will be trash characters printed along with the image.
Somehow, Android docs tells us that the limits of the value for a byte in a byte array is -128 and +127, when I tried to put in 255, Eclipse asked me to cast it to Byte.
Anyway, going back to nL and nW, for your case, you have an image with width 576, if we convert 576 to Binary, we get two bytes which would go like:
0000 0010 0100 0000
In this case, the Low Byte is 0100 0000 while the High Byte is 0000 0010. Convert it back to decimal and we get nL = 64 and nH = 2.
In my case, I printed an image that has width of 330px, converting 330 to binary we get:
0000 0001 0100 1010
In this case now, the Low Byte is 0100 1010 and the High Byte is 0000 0001. Converting to decimal, we get nL = 74 and nH = 1.
For more information, look at these documentation/tutorials:
Star Asia Mobile Printer Documentation
ECS-POS programming guide - really extensive
Another Documentation
The expanded version of the code above, with more explanation
Explanation of the code above
Hope these helps.

Solved!, I was doing a wrong printer initializing... The corect way is:
public static byte[] SELECT_BIT_IMAGE_MODE = {0x1B, 0x2A, 33, 255, 3};
So, by this way the image is printed completely fine

EDIT: Update based on reading your question: https://stackoverflow.com/questions/16597789/print-bitmap-on-esc-pos-printer-java
I will assume that the printer you are printing to is the same as above, i.e. the Rego Thermal Printer. This, as you note, support the ESC/POS Page Description Language.
Printers interpret data streamed to them as either a marked up document (in a similar way to how browser interpret HTML). In some cases, the printer literally runs the document as a program (eg PostScript). Link: Page Description Languages.
Common languages are:
Yours: ESC/POS.
PostScript
PCL
ZPL
You need to read the specifications for your printer to determine which language to use - if you need to support any printer, then you have a very large job ahead of you :(
In ESC/POS, you will need to use the GS v 0 command (documented on p33). You do this by sending the the characters 0x1D7630 across the serial link, followed by a set of arguments:
ASCII: Gs v 0
Decimal: 29 118 48 m xL xH yL yH [d]k
Hexadecimal: 1D 76 30 m xL xH yL yH [d]k
Parameter definitions:
m:
0,48: normal mode (1:1 scale)
1,49: double-width
2,50: double-height
3,51: double-width + double-height
xL, xH specifies (xL + xH × 256) bytes in horizontal direction for the bit image.
yL, yH specifies (yL + yH × 256) dots in vertical direction for the bit image.
[d]k specifies the bit image data (raster format).
k indicates the number of bit image data. k is an explanation parameter; therefore, it does not need to be transmitted.
Notes:
When data [d]k is 1 specifies a bit printed to 1 and not printed to 0.
If a raster bit image exceeds one line of print area, the excess data is not printed.
This command executes paper feed for amount needed for printing the bit image regardless of the settings by ESC 2 or ESC 3.
After printing the bit image, this command sets the print position to the beginning of the line, and clears up the buffer.
When this command is executed, the data is transmitted and printed synchronously. So no other printing command is required.
There are several more extensive expositions:
http://nicholas.piasecki.name/blog/2009/12/sending-a-bit-image-to-an-epson-tm-t88iii-receipt-printer-using-c-and-escpos/
On SO in C#. While not Java, it is close enough to be a template.
Unfortunately there is no printer API in Android. If you feel strongly about this, do follow these issues:
https://code.google.com/p/android/issues/detail?id=40486
https://code.google.com/p/android/issues/detail?id=1148

I am new to ESC/POS and am struggling with it. I came across this page which seems to have some useful functions: http://code.taobao.org/p/printer/src/trunk/prtest/src/com/enjar/plugins/PrintTools_58mm.java
It's in Chinese though, but might be worth going through. If anybody figures it out, I would like to get enlightened too...

I know for evolute and AMDL bluetooth printers.First Read the protocol defination document of the printer that tells you what specific bytes you need for the device-
public void connect() throws Exception
{
BluetoothDevice printer = BluetoothAdapter.getDefaultAdapter().getRemoteDevice(connParams);
Method m = printer.getClass().getMethod("createInsecureRfcommSocket",new Class[] { int.class });
sock = (BluetoothSocket)m.invoke(printer, Integer.valueOf(1));
sock.connect();
os=sock.getOutputStream();
in=sock.getInputStream();
}
After connecting through the above code you get the outputstream of the socket.Then convert your image to the corresponding byte through the tool provided with the printer you get something like
public byte[] Packet1={
(byte)0X8A,(byte)0XC6,(byte)0X94,(byte)0XF4,(byte)0X0B,(byte)0X5E,(byte)0X30,(byte)0X25,(byte)
0X01,(byte)0X5E,(byte)0X04,(byte)0X24,(byte)0X01,(byte)0X0C,(byte)0X5E,(byte)0X03,(byte)0X24,(byte)0X01,(byte)0X08,(byte)0X5E,(byte)0X27,(byte)0X25,(byte)
0X01,(byte)0X5E,(byte)0X04,(byte)0X24,(byte)0X05,(byte)0X0C,(byte)0X00,(byte)0X60,(byte)0X00,(byte)0X18,(byte)0X5E,(byte)0X27,(byte)0X25,(byte)
0X01,(byte)0X5E,(byte)0X03,(byte)0X24,(byte)0X06,(byte)0X30,(byte)0X1E,(byte)0X10,(byte)0X60,(byte)0X00,(byte)0X18,(byte)0X5E,(byte)0X27,(byte)0X25,(byte)
0X01,(byte)0X5E,(byte)0X03,(byte)0X24,(byte)0X06,(byte)0X70,(byte)0X3F,(byte)0X18,(byte)0XF0,(byte)0X00,(byte)0X3E,(byte)0X5E,(byte)0X27,(byte)0X25,(byte)
0X01,(byte)0X5E,(byte)0X03,(byte)0X24,(byte)0X06,(byte)0X70,(byte)0X3C,(byte)0X39,(byte)0XF1,(byte)0X80,(byte)0X3E,(byte)0X5E,(byte)0X27,(byte)0X25,(byte)
0X01,(byte)0X5E,(byte)0X03,(byte)0X24,(byte)0X06,(byte)0XF8,(byte)0X7C,(byte)0X9F,(byte)0XF1,(byte)0X80,(byte)0X7F,(byte)0X5E,(byte)0X27,(byte)0X25,(byte)
0X01,(byte)0X5E,(byte)0X03,(byte)0X24,(byte)0X06,(byte)0XF9,(byte)0X9E,(byte)0X1C,(byte)0XFF,(byte)0XC2,(byte)0X7E,(byte)0X5E,(byte)0X27,(byte)0X25,(byte)
0X01,(byte)0X5E,(byte)0X03,(byte)0X24,(byte)0X06,(byte)0XF9,(byte)0X9E,(byte)0X1C,(byte)0XE7,(byte)0XE2,(byte)0X7E,(byte)0X5E,(byte)0X27,(byte)0X25,(byte)
0X01,(byte)0X5E,(byte)0X03,(byte)0X24,(byte)0X06,(byte)0XFB,(byte)0X1E,(byte)0X1C,(byte)0XFF,(byte)0XE7,(byte)0XBE,(byte)0X5E,(byte)0X27,(byte)0X25,(byte)
0X01,(byte)0X5E,(byte)0X03,(byte)0X24,(byte)0X06,(byte)0X7B,(byte)0X16,(byte)0X1C,(byte)0XFF,(byte)0XDF,(byte)0X3E,(byte)0X5E,(byte)0X27,(byte)0X25,(byte)
0X01,(byte)0X5E,(byte)0X03,(byte)0X24,(byte)0X06,(byte)0X71,(byte)0X12,(byte)0X1C,(byte)0XE7,(byte)0XF7,(byte)0X34,(byte)0X5E,(byte)0X27,(byte)0X25,(byte)
0X01,(byte)0X5E,(byte)0X03,(byte)0X24,(byte)0X06,(byte)0X51,(byte)0X12,(byte)0X1C,(byte)0XF7,(byte)0XF7,(byte)0X24,(byte)0X5E,(byte)0X27,(byte)0X25,(byte)
0X01,(byte)0X5E,(byte)0X03,(byte)0X24,(byte)0X06,(byte)0X49,(byte)0X12,(byte)0X1C,(byte)0XFF,(byte)0XF3,(byte)0X24,(byte)0X5E,(byte)0X27,(byte)0X25,(byte)
0X01,(byte)0X5E,(byte)0X03,(byte)0X24,(byte)0X06,(byte)0X49,(byte)0X12,(byte)0X3F,(byte)0XFD,(byte)0XF3,(byte)0X24,(byte)0X5E,(byte)0X27,(byte)0X25,(byte)
0X01,(byte)0X5E,(byte)0X03,(byte)0X24,(byte)0X06,(byte)0X49,(byte)0X96,(byte)0X3F,(byte)0XFC,(byte)0XF3,(byte)0X24,(byte)0X5E,(byte)0X27,(byte)0X25,(byte)
0X01,(byte)0X5E,(byte)0X03,(byte)0X24,(byte)0X05,(byte)0X49,(byte)0X80,(byte)0X00,(byte)0X08,(byte)0X10,(byte)0X5E,(byte)0X28,(byte)0X25,(byte)
0X01,(byte)0X5E,(byte)0X30,(byte)0X25,(byte)
0X01,(byte)0X5E,(byte)0X03,(byte)0X24,(byte)0X06,(byte)0XE0,(byte)0X74,(byte)0XA9,(byte)0X33,(byte)0X23,(byte)0X26,(byte)0X5E,(byte)0X27,(byte)0X25,(byte)0X04
};
where 8A is starting byte C6 is mode byte (different for smart card , swipe and fingerprint) , 94 is font byte and last byte 04 is the end byte telling the hardware that this is end of the packet.Depending on size of the image you get several of these packets of length 256 byte (most printer).Write them to the outputStream.
os.write(Packet1)

This works for me:
BitmapFactory.Options options = new BitmapFactory.Options();
options.inTargetDensity = 200;
options.inDensity = 200;
Bitmap bmp = BitmapFactory.decodeResource(context.getResources(), img, options);
Before using the BitmapFactory.Options, I was able to print only 60X60 image size, now i can print images of greater size as well.

use this code:
public static void print(Context context) {
String examplePath = "file:///sdcard/dcim/Camera/20111210_181524.jpg";
Intent sendIntent = new Intent(Intent.ACTION_SEND);
sendIntent.setType("image/jpeg");
sendIntent.putExtra(Intent.EXTRA_SUBJECT, "Photo");
sendIntent.putExtra(Intent.EXTRA_STREAM, Uri.parse(examplePath));
sendIntent.putExtra(Intent.EXTRA_TEXT, "Enjoy the photo");
context.startActivity(Intent.createChooser(sendIntent, "Email:"));
}

Finding the color at coordinates in a PNG image in Java

With a URL of a PNG image (or the data at that url, in String form), how could one use Java to find the RGB (or similar) value at a set of coordinates?
Thanks in advance!

This example should have all you need:
http://www.daniweb.com/software-development/java/threads/114513
To cite the relevant part of the thread:
File inputFile = new File("image.png");
BufferedImage bufferedImage = ImageIO.read(inputFile);
int w = bufferedImage.getWidth();
int h = bufferedImage.getHeight(null);
//Get Pixels
int [] rgbs = new int[w*h];
bufferedImage.getRGB(0, 0, w, h, rgbs, 0, w); //Get all pixels
and then to get a particular pixel, see the docs:
http://docs.oracle.com/javase/6/docs/api/java/awt/image/BufferedImage.html#getRGB(int,%20int,%20int,%20int,%20int%91%93,%20int,%20int)
i.e.:
int pixel = rgbs[offset + (y-startY)*scansize + (x-startX)];
If you just want one pixel, you can use getRGB(x, y):
http://docs.oracle.com/javase/6/docs/api/java/awt/image/BufferedImage.html#getRGB(int,%20int)
i.e.:
int pixel = bufferedImage.getRGB(x, y);