JavaFX PixelReader Alpha-Channel not working

JavaFX PixelReader Alpha-Channel not working - java

public class Loader {
public static byte[] loadImage(String path) {
Image image;
try {
image = new Image(new FileInputStream(path));
int width = (int) image.getWidth();
int height = (int) image.getHeight();
byte[] data = new byte[width * height * 4];
image.getPixelReader().getPixels(0, 0, width, height, PixelFormat.getByteBgraPreInstance(), data, 0, width * 4);
return data;
}catch(IOException e) {
e.printStackTrace();
System.exit(-1);
}
return null;
}
}
#Override
public void render(GraphicsContext gc) {
gc.clearRect(0, 0, width, height);
gc.getPixelWriter().setPixels(x++, 0, 819 ,720, PixelFormat.getByteBgraPreInstance(), data, 0, 819*4);
gc.getPixelWriter().setPixels(400, 0,819 ,720, PixelFormat.getByteBgraPreInstance(), data, 0, 819*4);
}
Hello, at the moment i have a Problem with the PixelWriter/PixelReader from JavaFx. I try to read the Pixel from an Image and store it in a Buffer, after that I want to render it to the Screen. But the Image contains now no Alpha Value, so there are nor transparent Pixels. I searched for a few hours on the Internet but I can't find an answer. Maybe there is a problem with the Format.
Thanks in advance.

I haven't tried it (because you did not provide a complete and executable example) but I think your problem is that you use a pixel format with pre-multiplied alpha. Try again with one of the simple rgb formats without pre-multiplication.

Related

byte array to BufferedImage or DecodedImage at Android

I want to use the function below at Android but ImageIO.read function can not be use at Android.
DecodedImage decode(byte[] image) {
return Exceptions.sneak().get(() -> {
BufferedImage buffered = ImageIO.read(new ByteArrayInputStream(image));
if (buffered == null)
throw new IllegalArgumentException("Unsupported image format.");
int width = buffered.getWidth();
int height = buffered.getHeight();
int[] pixels = new int[width * height];
buffered.getRGB(0, 0, width, height, pixels, 0, width);
return new DecodedImage(width, height, pixels);
});
}
Is there any equivalent function to do this operation in Java for Android?

Merge two images with different size so that they overlap correctly

I have two images with different sizes. I want to merge these two images so that the front images overlays correctly the background image.
background (width:144 height:147):
front: (width:227 height:238)
Currently my result looks like this, but i need it to overlay perfectly
My approach is.
I am resizing the smaller image to the bigger one. For that I am using the a external lib named imgscalr (https://mvnrepository.com/artifact/org.imgscalr/imgscalr-lib/4.2).
As you can see result image is not correct, so I tried to scale the front image so that it overlay the background, also I changed the root of the x / y when I draw the front image on the background but i still have a difference. Any idea how I can merge the two images, so that the strokes image (front) overlays the background.
public static byte[] mergeBackgroundWithStrokes(byte[] backgroundImage, byte[] frontImage)
throws IOException, PDProcessingException {
Path backgroundfile = readAllBytes(backgroundImage, "background");
Path outputFile = Files.createTempFile("output", ".png");
BufferedImage backgroundBuffImg = ImageIO.read(backgroundfile.toFile());
BufferedImage frontBuffImg = makeColorTransparent(frontImage, Color.WHITE);
int width = Math.max(backgroundBuffImg.getWidth(), frontBuffImg.getWidth());
int height = Math.max(backgroundBuffImg.getHeight(), frontBuffImg.getHeight());
backgroundBuffImg = resize(backgroundBuffImg, width, height);
//scaling front image
int scaledWidth = (int) ((width));
int scaledHeight = (int) ((height) * 1.02);
frontBuffImg = resize(frontBuffImg, scaledWidth, scaledHeight);
BufferedImage newImage = mergeImages(backgroundBuffImg, frontBuffImg);
ImageIO.write(newImage, "PNG", outputFile.toFile());
return Files.readAllBytes(outputFile);
}
public static BufferedImage resize(BufferedImage img, int width, int height)
{
if (img.getWidth() == width && img.getHeight() == height) {
return img;
} else {
return Scalr.resize(img, width, height);
}
}
public static BufferedImage mergeImages(BufferedImage background, BufferedImage front) {
int width = background.getWidth();
int height = background.getHeight();
BufferedImage newImage = new BufferedImage(width, height, BufferedImage.TYPE_INT_ARGB);
Graphics g = newImage.getGraphics();
g.drawImage(background, 0, 0, null);
g.drawImage(front, 15, -10, background.getWidth(), background.getHeight(), 0, 0, width, height, null);
return newImage;
}
Here you can see the complete class: https://pastebin.com/F4VrBwRv

Antialiasing on JButton Icon [duplicate]

I made this code to resize images with two factors. It works, but the quality of image is very bad after it is resized! Can you help me?
This is the code
public class ImageTest {
private static final int factor1 = 3;
private static final int factor2 = 4;
public static void main(String [] args){
JFileChooser cs = new JFileChooser();
cs.setFileSelectionMode(cs.DIRECTORIES_ONLY);
int i = cs.showOpenDialog(null);
if(i==cs.APPROVE_OPTION){
File f = cs.getSelectedFile();
File[] ff = f.listFiles();
for(int j=0;j<ff.length;j++){
String end = ff[j].getName().substring(ff[j].getName().indexOf(".")+1);
System.out.println(end);
try{
BufferedImage originalImage = ImageIO.read(ff[j]);
int type = originalImage.getType() == 0? BufferedImage.TYPE_INT_ARGB : originalImage.getType();
BufferedImage resizeImageJpg = resizeImageWithHint(originalImage, type);
ImageIO.write(resizeImageJpg, end, new File("pr/"+ff[j].getName()));
}catch(IOException e){
e.printStackTrace();
}
}
}
}
private static BufferedImage resizeImageWithHint(BufferedImage originalImage, int type){
int IMG_WIDTH = (originalImage.getWidth()*factor1)/factor2;
int IMG_HEIGHT = (originalImage.getHeight()*factor1)/factor2;
BufferedImage resizedImage = new BufferedImage(IMG_WIDTH, IMG_HEIGHT, type);
Graphics2D g = resizedImage.createGraphics();
g.drawImage(originalImage, 0, 0, IMG_WIDTH, IMG_HEIGHT, null);
g.dispose();
g.setComposite(AlphaComposite.Src);
g.setRenderingHint(RenderingHints.KEY_INTERPOLATION,
RenderingHints.VALUE_INTERPOLATION_BILINEAR);
g.setRenderingHint(RenderingHints.KEY_RENDERING,
RenderingHints.VALUE_RENDER_QUALITY);
g.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
RenderingHints.VALUE_ANTIALIAS_ON);
return resizedImage;
}
}
I saw on web that resizeImageWithHint is done within the scope so as not to lose quality.. but it does! why? can you help me with this?

The best article I have ever read on this topic is The Perils of Image.getScaledInstance() (web archive).
In short: You need to use several resizing steps in order to get a good image. Helper method from the article:
public BufferedImage getScaledInstance(BufferedImage img,
int targetWidth,
int targetHeight,
Object hint,
boolean higherQuality)
{
int type = (img.getTransparency() == Transparency.OPAQUE) ?
BufferedImage.TYPE_INT_RGB : BufferedImage.TYPE_INT_ARGB;
BufferedImage ret = (BufferedImage)img;
int w, h;
if (higherQuality) {
// Use multi-step technique: start with original size, then
// scale down in multiple passes with drawImage()
// until the target size is reached
w = img.getWidth();
h = img.getHeight();
} else {
// Use one-step technique: scale directly from original
// size to target size with a single drawImage() call
w = targetWidth;
h = targetHeight;
}
do {
if (higherQuality && w > targetWidth) {
w /= 2;
if (w < targetWidth) {
w = targetWidth;
}
}
if (higherQuality && h > targetHeight) {
h /= 2;
if (h < targetHeight) {
h = targetHeight;
}
}
BufferedImage tmp = new BufferedImage(w, h, type);
Graphics2D g2 = tmp.createGraphics();
g2.setRenderingHint(RenderingHints.KEY_INTERPOLATION, hint);
g2.drawImage(ret, 0, 0, w, h, null);
g2.dispose();
ret = tmp;
} while (w != targetWidth || h != targetHeight);
return ret;
}

The following code produced me highest quality resize with aspect ratio preserved.
Tried few things and read several entries presented here in other answers. Lost two days and in the end I got the best result with plain Java method (tried also ImageMagick and java-image-scaling libraries):
public static boolean resizeUsingJavaAlgo(String source, File dest, int width, int height) throws IOException {
BufferedImage sourceImage = ImageIO.read(new FileInputStream(source));
double ratio = (double) sourceImage.getWidth()/sourceImage.getHeight();
if (width < 1) {
width = (int) (height * ratio + 0.4);
} else if (height < 1) {
height = (int) (width /ratio + 0.4);
}
Image scaled = sourceImage.getScaledInstance(width, height, Image.SCALE_AREA_AVERAGING);
BufferedImage bufferedScaled = new BufferedImage(scaled.getWidth(null), scaled.getHeight(null), BufferedImage.TYPE_INT_RGB);
Graphics2D g2d = bufferedScaled.createGraphics();
g2d.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BICUBIC);
g2d.drawImage(scaled, 0, 0, width, height, null);
dest.createNewFile();
writeJpeg(bufferedScaled, dest.getCanonicalPath(), 1.0f);
return true;
}
/**
* Write a JPEG file setting the compression quality.
*
* #param image a BufferedImage to be saved
* #param destFile destination file (absolute or relative path)
* #param quality a float between 0 and 1, where 1 means uncompressed.
* #throws IOException in case of problems writing the file
*/
private static void writeJpeg(BufferedImage image, String destFile, float quality)
throws IOException {
ImageWriter writer = null;
FileImageOutputStream output = null;
try {
writer = ImageIO.getImageWritersByFormatName("jpeg").next();
ImageWriteParam param = writer.getDefaultWriteParam();
param.setCompressionMode(ImageWriteParam.MODE_EXPLICIT);
param.setCompressionQuality(quality);
output = new FileImageOutputStream(new File(destFile));
writer.setOutput(output);
IIOImage iioImage = new IIOImage(image, null, null);
writer.write(null, iioImage, param);
} catch (IOException ex) {
throw ex;
} finally {
if (writer != null) {
writer.dispose();
}
if (output != null) {
output.close();
}
}
}

Know question is old... I've tried different solutions surfing then web, I got the best result using getScaledInstance(), supplying Image.SCALE_SMOOTH as argument. In fact the resulting image quality was really better.
My code below:
final int THUMB_SIDE = 140;
try {
BufferedImage masterImage = ImageIO.read(startingImage);
BufferedImage thumbImage = new BufferedImage(THUMB_SIDE, THUMB_SIDE, BufferedImage.TYPE_INT_ARGB);
Graphics2D g2d = thumbImage.createGraphics();
g2d.drawImage(masterImage.getScaledInstance(THUMB_SIDE, THUMB_SIDE, Image.SCALE_SMOOTH), 0, 0, THUMB_SIDE, THUMB_SIDE, null);
g2d.dispose();
String thumb_path = path.substring(0, path.indexOf(".png")) + "_thumb.png";
ImageIO.write(thumbImage, "png", new File(thumb_path));
} catch (IOException e) {
e.printStackTrace();
}

If your image source is a png then use like this:
Image imgSmall = imgBig.getScaledInstance(
targetWidth, targetHeight, Image.SCALE_SMOOTH);
If you want to resize jpeg or gif without loose too much quality, I made a library in 2010 for this: beautylib on github that uses internally this other library: java-image-scaling. You can see directly the source code to find something useful: https://github.com/felipelalli/beautylib/blob/master/src/br/eti/fml/beautylib/ResizeImage.java

None of the answers will help you to get real quality you desire. Include thumbailator.jar in your project (download it form here):
https://code.google.com/p/thumbnailator/
https://code.google.com/p/thumbnailator/wiki/Downloads?tm=2
Then upload the image first (as file, without Thumbnailator - it's use is to create thumbs, but you can create large images with it of course), and resize it to every dimensions you want (with Thumbnailator 800x600 for example). Quality will be very good. I was searching for this long time, this .jar helped me to achieve what i want.

Yes, I had the same problems and solved them, please read my question (answer is embedded in the question). I tried imgscalr and java-image-scaling libraries and found the second much better quality. Get close to the monitor to appreciate the difference between the thumbnail examples.
Despite my initial thoughts, resizing an image seems a very complicate thing, you don't want to do it yourself. For example I tell java-image-scaling to use ResampleFilters.getLanczos3Filter() to have better result.
It also addresses how to save a JPG with a quality higher than the standard 75, which produces a bad result especially for a thumbnail.
I also wrote a small class, called MyImage to help with common tasks, such as reading an image from a byte array, from a file, scaling by specifying only width or only height, scaling by specifying a bounding box, scaling by specifying width and height and adding a white band to make the image not distorted and writing to JPG file.

Answer: Remove the hints VALUE_INTERPOLATION_BILINEAR, and VALUE_RENDERING_QUALITY.
Example:
public static BufferedImage resizeImage(BufferedImage image, int width, int height) {
// Temporary image
BufferedImage tmp = image;
// Result image
BufferedImage result = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
// Graphics object
Graphics2D graphics = (Graphics2D)result.createGraphics();
// Add rendering hints
graphics.setRenderingHint(RenderingHints.KEY_COLOR_RENDERING, RenderingHints.VALUE_COLOR_RENDER_QUALITY);
graphics.setRenderingHint(RenderingHints.KEY_DITHERING, RenderingHints.VALUE_DITHER_ENABLE);
// Draw tmp
graphics.drawImage(tmp, 0, 0, width, height, null);
// Dispose of graphics object
graphics.dispose();
// Return image result
return result;
}
Note: For some reason, the hints VALUE_INTERPOLATION_BILINEAR and VALUE_RENDERING_QUALITY blur the image being resized.

All the methods posted does'nt work for me i have to reduce QrCode size, but with above methods the quality is poor and scanner doesn't work , if i take original picture and resize it in paint the scanner is working.

The do while loop used in The Perils of Image.getScaledInstance() will run into an infinite loop, given those values,
w = 606; h = 505, targetWidth = 677, targetHeight = 505
Here is a simplied testing code, you can try it.
public class LoopTest {
public static void main(String[] args) {
new LoopTest(true, 606, 505, 677, 505);
}
public LoopTest(boolean higherQuality, int w, int h, int targetWidth, int targetHeight) {
do {
if (higherQuality && w > targetWidth) {
w /= 2;
if (w < targetWidth) {
w = targetWidth;
}
}
if (higherQuality && h > targetHeight) {
h /= 2;
if (h < targetHeight) {
h = targetHeight;
}
}
} while (w != targetWidth || h != targetHeight); // TODO Auto-generated constructor stub
}
}
A quick work around: define an index for loop count. If the index is >=10, break out of loop.

Is there the better way to resize the Buffered image without losing of quality? [duplicate]

I made this code to resize images with two factors. It works, but the quality of image is very bad after it is resized! Can you help me?
This is the code
public class ImageTest {
private static final int factor1 = 3;
private static final int factor2 = 4;
public static void main(String [] args){
JFileChooser cs = new JFileChooser();
cs.setFileSelectionMode(cs.DIRECTORIES_ONLY);
int i = cs.showOpenDialog(null);
if(i==cs.APPROVE_OPTION){
File f = cs.getSelectedFile();
File[] ff = f.listFiles();
for(int j=0;j<ff.length;j++){
String end = ff[j].getName().substring(ff[j].getName().indexOf(".")+1);
System.out.println(end);
try{
BufferedImage originalImage = ImageIO.read(ff[j]);
int type = originalImage.getType() == 0? BufferedImage.TYPE_INT_ARGB : originalImage.getType();
BufferedImage resizeImageJpg = resizeImageWithHint(originalImage, type);
ImageIO.write(resizeImageJpg, end, new File("pr/"+ff[j].getName()));
}catch(IOException e){
e.printStackTrace();
}
}
}
}
private static BufferedImage resizeImageWithHint(BufferedImage originalImage, int type){
int IMG_WIDTH = (originalImage.getWidth()*factor1)/factor2;
int IMG_HEIGHT = (originalImage.getHeight()*factor1)/factor2;
BufferedImage resizedImage = new BufferedImage(IMG_WIDTH, IMG_HEIGHT, type);
Graphics2D g = resizedImage.createGraphics();
g.drawImage(originalImage, 0, 0, IMG_WIDTH, IMG_HEIGHT, null);
g.dispose();
g.setComposite(AlphaComposite.Src);
g.setRenderingHint(RenderingHints.KEY_INTERPOLATION,
RenderingHints.VALUE_INTERPOLATION_BILINEAR);
g.setRenderingHint(RenderingHints.KEY_RENDERING,
RenderingHints.VALUE_RENDER_QUALITY);
g.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
RenderingHints.VALUE_ANTIALIAS_ON);
return resizedImage;
}
}
I saw on web that resizeImageWithHint is done within the scope so as not to lose quality.. but it does! why? can you help me with this?

The best article I have ever read on this topic is The Perils of Image.getScaledInstance() (web archive).
In short: You need to use several resizing steps in order to get a good image. Helper method from the article:
public BufferedImage getScaledInstance(BufferedImage img,
int targetWidth,
int targetHeight,
Object hint,
boolean higherQuality)
{
int type = (img.getTransparency() == Transparency.OPAQUE) ?
BufferedImage.TYPE_INT_RGB : BufferedImage.TYPE_INT_ARGB;
BufferedImage ret = (BufferedImage)img;
int w, h;
if (higherQuality) {
// Use multi-step technique: start with original size, then
// scale down in multiple passes with drawImage()
// until the target size is reached
w = img.getWidth();
h = img.getHeight();
} else {
// Use one-step technique: scale directly from original
// size to target size with a single drawImage() call
w = targetWidth;
h = targetHeight;
}
do {
if (higherQuality && w > targetWidth) {
w /= 2;
if (w < targetWidth) {
w = targetWidth;
}
}
if (higherQuality && h > targetHeight) {
h /= 2;
if (h < targetHeight) {
h = targetHeight;
}
}
BufferedImage tmp = new BufferedImage(w, h, type);
Graphics2D g2 = tmp.createGraphics();
g2.setRenderingHint(RenderingHints.KEY_INTERPOLATION, hint);
g2.drawImage(ret, 0, 0, w, h, null);
g2.dispose();
ret = tmp;
} while (w != targetWidth || h != targetHeight);
return ret;
}

The following code produced me highest quality resize with aspect ratio preserved.
Tried few things and read several entries presented here in other answers. Lost two days and in the end I got the best result with plain Java method (tried also ImageMagick and java-image-scaling libraries):
public static boolean resizeUsingJavaAlgo(String source, File dest, int width, int height) throws IOException {
BufferedImage sourceImage = ImageIO.read(new FileInputStream(source));
double ratio = (double) sourceImage.getWidth()/sourceImage.getHeight();
if (width < 1) {
width = (int) (height * ratio + 0.4);
} else if (height < 1) {
height = (int) (width /ratio + 0.4);
}
Image scaled = sourceImage.getScaledInstance(width, height, Image.SCALE_AREA_AVERAGING);
BufferedImage bufferedScaled = new BufferedImage(scaled.getWidth(null), scaled.getHeight(null), BufferedImage.TYPE_INT_RGB);
Graphics2D g2d = bufferedScaled.createGraphics();
g2d.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BICUBIC);
g2d.drawImage(scaled, 0, 0, width, height, null);
dest.createNewFile();
writeJpeg(bufferedScaled, dest.getCanonicalPath(), 1.0f);
return true;
}
/**
* Write a JPEG file setting the compression quality.
*
* #param image a BufferedImage to be saved
* #param destFile destination file (absolute or relative path)
* #param quality a float between 0 and 1, where 1 means uncompressed.
* #throws IOException in case of problems writing the file
*/
private static void writeJpeg(BufferedImage image, String destFile, float quality)
throws IOException {
ImageWriter writer = null;
FileImageOutputStream output = null;
try {
writer = ImageIO.getImageWritersByFormatName("jpeg").next();
ImageWriteParam param = writer.getDefaultWriteParam();
param.setCompressionMode(ImageWriteParam.MODE_EXPLICIT);
param.setCompressionQuality(quality);
output = new FileImageOutputStream(new File(destFile));
writer.setOutput(output);
IIOImage iioImage = new IIOImage(image, null, null);
writer.write(null, iioImage, param);
} catch (IOException ex) {
throw ex;
} finally {
if (writer != null) {
writer.dispose();
}
if (output != null) {
output.close();
}
}
}

Know question is old... I've tried different solutions surfing then web, I got the best result using getScaledInstance(), supplying Image.SCALE_SMOOTH as argument. In fact the resulting image quality was really better.
My code below:
final int THUMB_SIDE = 140;
try {
BufferedImage masterImage = ImageIO.read(startingImage);
BufferedImage thumbImage = new BufferedImage(THUMB_SIDE, THUMB_SIDE, BufferedImage.TYPE_INT_ARGB);
Graphics2D g2d = thumbImage.createGraphics();
g2d.drawImage(masterImage.getScaledInstance(THUMB_SIDE, THUMB_SIDE, Image.SCALE_SMOOTH), 0, 0, THUMB_SIDE, THUMB_SIDE, null);
g2d.dispose();
String thumb_path = path.substring(0, path.indexOf(".png")) + "_thumb.png";
ImageIO.write(thumbImage, "png", new File(thumb_path));
} catch (IOException e) {
e.printStackTrace();
}

If your image source is a png then use like this:
Image imgSmall = imgBig.getScaledInstance(
targetWidth, targetHeight, Image.SCALE_SMOOTH);
If you want to resize jpeg or gif without loose too much quality, I made a library in 2010 for this: beautylib on github that uses internally this other library: java-image-scaling. You can see directly the source code to find something useful: https://github.com/felipelalli/beautylib/blob/master/src/br/eti/fml/beautylib/ResizeImage.java

None of the answers will help you to get real quality you desire. Include thumbailator.jar in your project (download it form here):
https://code.google.com/p/thumbnailator/
https://code.google.com/p/thumbnailator/wiki/Downloads?tm=2
Then upload the image first (as file, without Thumbnailator - it's use is to create thumbs, but you can create large images with it of course), and resize it to every dimensions you want (with Thumbnailator 800x600 for example). Quality will be very good. I was searching for this long time, this .jar helped me to achieve what i want.

Yes, I had the same problems and solved them, please read my question (answer is embedded in the question). I tried imgscalr and java-image-scaling libraries and found the second much better quality. Get close to the monitor to appreciate the difference between the thumbnail examples.
Despite my initial thoughts, resizing an image seems a very complicate thing, you don't want to do it yourself. For example I tell java-image-scaling to use ResampleFilters.getLanczos3Filter() to have better result.
It also addresses how to save a JPG with a quality higher than the standard 75, which produces a bad result especially for a thumbnail.
I also wrote a small class, called MyImage to help with common tasks, such as reading an image from a byte array, from a file, scaling by specifying only width or only height, scaling by specifying a bounding box, scaling by specifying width and height and adding a white band to make the image not distorted and writing to JPG file.

Answer: Remove the hints VALUE_INTERPOLATION_BILINEAR, and VALUE_RENDERING_QUALITY.
Example:
public static BufferedImage resizeImage(BufferedImage image, int width, int height) {
// Temporary image
BufferedImage tmp = image;
// Result image
BufferedImage result = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
// Graphics object
Graphics2D graphics = (Graphics2D)result.createGraphics();
// Add rendering hints
graphics.setRenderingHint(RenderingHints.KEY_COLOR_RENDERING, RenderingHints.VALUE_COLOR_RENDER_QUALITY);
graphics.setRenderingHint(RenderingHints.KEY_DITHERING, RenderingHints.VALUE_DITHER_ENABLE);
// Draw tmp
graphics.drawImage(tmp, 0, 0, width, height, null);
// Dispose of graphics object
graphics.dispose();
// Return image result
return result;
}
Note: For some reason, the hints VALUE_INTERPOLATION_BILINEAR and VALUE_RENDERING_QUALITY blur the image being resized.

All the methods posted does'nt work for me i have to reduce QrCode size, but with above methods the quality is poor and scanner doesn't work , if i take original picture and resize it in paint the scanner is working.

The do while loop used in The Perils of Image.getScaledInstance() will run into an infinite loop, given those values,
w = 606; h = 505, targetWidth = 677, targetHeight = 505
Here is a simplied testing code, you can try it.
public class LoopTest {
public static void main(String[] args) {
new LoopTest(true, 606, 505, 677, 505);
}
public LoopTest(boolean higherQuality, int w, int h, int targetWidth, int targetHeight) {
do {
if (higherQuality && w > targetWidth) {
w /= 2;
if (w < targetWidth) {
w = targetWidth;
}
}
if (higherQuality && h > targetHeight) {
h /= 2;
if (h < targetHeight) {
h = targetHeight;
}
}
} while (w != targetWidth || h != targetHeight); // TODO Auto-generated constructor stub
}
}
A quick work around: define an index for loop count. If the index is >=10, break out of loop.

Re-sizing an image without losing quality

I made this code to resize images with two factors. It works, but the quality of image is very bad after it is resized! Can you help me?
This is the code
public class ImageTest {
private static final int factor1 = 3;
private static final int factor2 = 4;
public static void main(String [] args){
JFileChooser cs = new JFileChooser();
cs.setFileSelectionMode(cs.DIRECTORIES_ONLY);
int i = cs.showOpenDialog(null);
if(i==cs.APPROVE_OPTION){
File f = cs.getSelectedFile();
File[] ff = f.listFiles();
for(int j=0;j<ff.length;j++){
String end = ff[j].getName().substring(ff[j].getName().indexOf(".")+1);
System.out.println(end);
try{
BufferedImage originalImage = ImageIO.read(ff[j]);
int type = originalImage.getType() == 0? BufferedImage.TYPE_INT_ARGB : originalImage.getType();
BufferedImage resizeImageJpg = resizeImageWithHint(originalImage, type);
ImageIO.write(resizeImageJpg, end, new File("pr/"+ff[j].getName()));
}catch(IOException e){
e.printStackTrace();
}
}
}
}
private static BufferedImage resizeImageWithHint(BufferedImage originalImage, int type){
int IMG_WIDTH = (originalImage.getWidth()*factor1)/factor2;
int IMG_HEIGHT = (originalImage.getHeight()*factor1)/factor2;
BufferedImage resizedImage = new BufferedImage(IMG_WIDTH, IMG_HEIGHT, type);
Graphics2D g = resizedImage.createGraphics();
g.drawImage(originalImage, 0, 0, IMG_WIDTH, IMG_HEIGHT, null);
g.dispose();
g.setComposite(AlphaComposite.Src);
g.setRenderingHint(RenderingHints.KEY_INTERPOLATION,
RenderingHints.VALUE_INTERPOLATION_BILINEAR);
g.setRenderingHint(RenderingHints.KEY_RENDERING,
RenderingHints.VALUE_RENDER_QUALITY);
g.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
RenderingHints.VALUE_ANTIALIAS_ON);
return resizedImage;
}
}
I saw on web that resizeImageWithHint is done within the scope so as not to lose quality.. but it does! why? can you help me with this?

The best article I have ever read on this topic is The Perils of Image.getScaledInstance() (web archive).
In short: You need to use several resizing steps in order to get a good image. Helper method from the article:
public BufferedImage getScaledInstance(BufferedImage img,
int targetWidth,
int targetHeight,
Object hint,
boolean higherQuality)
{
int type = (img.getTransparency() == Transparency.OPAQUE) ?
BufferedImage.TYPE_INT_RGB : BufferedImage.TYPE_INT_ARGB;
BufferedImage ret = (BufferedImage)img;
int w, h;
if (higherQuality) {
// Use multi-step technique: start with original size, then
// scale down in multiple passes with drawImage()
// until the target size is reached
w = img.getWidth();
h = img.getHeight();
} else {
// Use one-step technique: scale directly from original
// size to target size with a single drawImage() call
w = targetWidth;
h = targetHeight;
}
do {
if (higherQuality && w > targetWidth) {
w /= 2;
if (w < targetWidth) {
w = targetWidth;
}
}
if (higherQuality && h > targetHeight) {
h /= 2;
if (h < targetHeight) {
h = targetHeight;
}
}
BufferedImage tmp = new BufferedImage(w, h, type);
Graphics2D g2 = tmp.createGraphics();
g2.setRenderingHint(RenderingHints.KEY_INTERPOLATION, hint);
g2.drawImage(ret, 0, 0, w, h, null);
g2.dispose();
ret = tmp;
} while (w != targetWidth || h != targetHeight);
return ret;
}

The following code produced me highest quality resize with aspect ratio preserved.
Tried few things and read several entries presented here in other answers. Lost two days and in the end I got the best result with plain Java method (tried also ImageMagick and java-image-scaling libraries):
public static boolean resizeUsingJavaAlgo(String source, File dest, int width, int height) throws IOException {
BufferedImage sourceImage = ImageIO.read(new FileInputStream(source));
double ratio = (double) sourceImage.getWidth()/sourceImage.getHeight();
if (width < 1) {
width = (int) (height * ratio + 0.4);
} else if (height < 1) {
height = (int) (width /ratio + 0.4);
}
Image scaled = sourceImage.getScaledInstance(width, height, Image.SCALE_AREA_AVERAGING);
BufferedImage bufferedScaled = new BufferedImage(scaled.getWidth(null), scaled.getHeight(null), BufferedImage.TYPE_INT_RGB);
Graphics2D g2d = bufferedScaled.createGraphics();
g2d.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BICUBIC);
g2d.drawImage(scaled, 0, 0, width, height, null);
dest.createNewFile();
writeJpeg(bufferedScaled, dest.getCanonicalPath(), 1.0f);
return true;
}
/**
* Write a JPEG file setting the compression quality.
*
* #param image a BufferedImage to be saved
* #param destFile destination file (absolute or relative path)
* #param quality a float between 0 and 1, where 1 means uncompressed.
* #throws IOException in case of problems writing the file
*/
private static void writeJpeg(BufferedImage image, String destFile, float quality)
throws IOException {
ImageWriter writer = null;
FileImageOutputStream output = null;
try {
writer = ImageIO.getImageWritersByFormatName("jpeg").next();
ImageWriteParam param = writer.getDefaultWriteParam();
param.setCompressionMode(ImageWriteParam.MODE_EXPLICIT);
param.setCompressionQuality(quality);
output = new FileImageOutputStream(new File(destFile));
writer.setOutput(output);
IIOImage iioImage = new IIOImage(image, null, null);
writer.write(null, iioImage, param);
} catch (IOException ex) {
throw ex;
} finally {
if (writer != null) {
writer.dispose();
}
if (output != null) {
output.close();
}
}
}

Know question is old... I've tried different solutions surfing then web, I got the best result using getScaledInstance(), supplying Image.SCALE_SMOOTH as argument. In fact the resulting image quality was really better.
My code below:
final int THUMB_SIDE = 140;
try {
BufferedImage masterImage = ImageIO.read(startingImage);
BufferedImage thumbImage = new BufferedImage(THUMB_SIDE, THUMB_SIDE, BufferedImage.TYPE_INT_ARGB);
Graphics2D g2d = thumbImage.createGraphics();
g2d.drawImage(masterImage.getScaledInstance(THUMB_SIDE, THUMB_SIDE, Image.SCALE_SMOOTH), 0, 0, THUMB_SIDE, THUMB_SIDE, null);
g2d.dispose();
String thumb_path = path.substring(0, path.indexOf(".png")) + "_thumb.png";
ImageIO.write(thumbImage, "png", new File(thumb_path));
} catch (IOException e) {
e.printStackTrace();
}

If your image source is a png then use like this:
Image imgSmall = imgBig.getScaledInstance(
targetWidth, targetHeight, Image.SCALE_SMOOTH);
If you want to resize jpeg or gif without loose too much quality, I made a library in 2010 for this: beautylib on github that uses internally this other library: java-image-scaling. You can see directly the source code to find something useful: https://github.com/felipelalli/beautylib/blob/master/src/br/eti/fml/beautylib/ResizeImage.java

None of the answers will help you to get real quality you desire. Include thumbailator.jar in your project (download it form here):
https://code.google.com/p/thumbnailator/
https://code.google.com/p/thumbnailator/wiki/Downloads?tm=2
Then upload the image first (as file, without Thumbnailator - it's use is to create thumbs, but you can create large images with it of course), and resize it to every dimensions you want (with Thumbnailator 800x600 for example). Quality will be very good. I was searching for this long time, this .jar helped me to achieve what i want.

Yes, I had the same problems and solved them, please read my question (answer is embedded in the question). I tried imgscalr and java-image-scaling libraries and found the second much better quality. Get close to the monitor to appreciate the difference between the thumbnail examples.
Despite my initial thoughts, resizing an image seems a very complicate thing, you don't want to do it yourself. For example I tell java-image-scaling to use ResampleFilters.getLanczos3Filter() to have better result.
It also addresses how to save a JPG with a quality higher than the standard 75, which produces a bad result especially for a thumbnail.
I also wrote a small class, called MyImage to help with common tasks, such as reading an image from a byte array, from a file, scaling by specifying only width or only height, scaling by specifying a bounding box, scaling by specifying width and height and adding a white band to make the image not distorted and writing to JPG file.

Answer: Remove the hints VALUE_INTERPOLATION_BILINEAR, and VALUE_RENDERING_QUALITY.
Example:
public static BufferedImage resizeImage(BufferedImage image, int width, int height) {
// Temporary image
BufferedImage tmp = image;
// Result image
BufferedImage result = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
// Graphics object
Graphics2D graphics = (Graphics2D)result.createGraphics();
// Add rendering hints
graphics.setRenderingHint(RenderingHints.KEY_COLOR_RENDERING, RenderingHints.VALUE_COLOR_RENDER_QUALITY);
graphics.setRenderingHint(RenderingHints.KEY_DITHERING, RenderingHints.VALUE_DITHER_ENABLE);
// Draw tmp
graphics.drawImage(tmp, 0, 0, width, height, null);
// Dispose of graphics object
graphics.dispose();
// Return image result
return result;
}
Note: For some reason, the hints VALUE_INTERPOLATION_BILINEAR and VALUE_RENDERING_QUALITY blur the image being resized.

All the methods posted does'nt work for me i have to reduce QrCode size, but with above methods the quality is poor and scanner doesn't work , if i take original picture and resize it in paint the scanner is working.

The do while loop used in The Perils of Image.getScaledInstance() will run into an infinite loop, given those values,
w = 606; h = 505, targetWidth = 677, targetHeight = 505
Here is a simplied testing code, you can try it.
public class LoopTest {
public static void main(String[] args) {
new LoopTest(true, 606, 505, 677, 505);
}
public LoopTest(boolean higherQuality, int w, int h, int targetWidth, int targetHeight) {
do {
if (higherQuality && w > targetWidth) {
w /= 2;
if (w < targetWidth) {
w = targetWidth;
}
}
if (higherQuality && h > targetHeight) {
h /= 2;
if (h < targetHeight) {
h = targetHeight;
}
}
} while (w != targetWidth || h != targetHeight); // TODO Auto-generated constructor stub
}
}
A quick work around: define an index for loop count. If the index is >=10, break out of loop.

Develop Reference

Java is a programming language and computing platform first released by Sun Microsystems in 1995.

JavaFX PixelReader Alpha-Channel not working - java

I haven't tried it (because you did not provide a complete and executable example) but I think your problem is that you use a pixel format with pre-multiplied alpha. Try again with one of the simple rgb formats without pre-multiplication.

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