调整 Java 映像大小，保持高宽比

我有一个图像，我调整大小:

if((width != null) || (height != null))
{
try{
// scale image on disk
BufferedImage originalImage = ImageIO.read(file);
int type = originalImage.getType() == 0? BufferedImage.TYPE_INT_ARGB
: originalImage.getType();


BufferedImage resizeImageJpg = resizeImage(originalImage, type, 200, 200);
ImageIO.write(resizeImageJpg, "jpg", file);


} catch(IOException e) {
System.out.println(e.getMessage());
}
}

我是这样调整图像大小的:

private static BufferedImage resizeImage(BufferedImage originalImage, int type,
Integer img_width, Integer img_height)
{
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();


return resizedImage;
}

现在的问题是，我还需要保持高宽比。也就是说，我需要新的200/200图像包含新的图像缩放。就像这样: enter image description here

我尝试了一些方法，但效果不如预期。 感谢你的帮助，非常感谢。

125563 次浏览
小开
最佳答案

Here we go:

Dimension imgSize = new Dimension(500, 100);
Dimension boundary = new Dimension(200, 200);

Function to return the new size depending on the boundary:

public static Dimension getScaledDimension(Dimension imgSize, Dimension boundary) {


int original_width = imgSize.width;
int original_height = imgSize.height;
int bound_width = boundary.width;
int bound_height = boundary.height;
int new_width = original_width;
int new_height = original_height;


// first check if we need to scale width
if (original_width > bound_width) {
//scale width to fit
new_width = bound_width;
//scale height to maintain aspect ratio
new_height = (new_width * original_height) / original_width;
}


// then check if we need to scale even with the new height
if (new_height > bound_height) {
//scale height to fit instead
new_height = bound_height;
//scale width to maintain aspect ratio
new_width = (new_height * original_width) / original_height;
}


return new Dimension(new_width, new_height);
}

In case anyone also needs the image resizing code, here is a decent solution.

If you're unsure about the above solution, there are different ways to achieve the same result.

小开

You will want to check out Image.getScaledInstance(), and more in this answer: How to improve the performance of g.drawImage() method for resizing images

小开

try this

float rateX =  (float)jpDisplayImagen.getWidth()/(float)img.getWidth();
float rateY = (float)jpDisplayImagen.getHeight()/(float)img.getHeight();
if (rateX>rateY){
int W=(int)(img.getWidth()*rateY);
int H=(int)(img.getHeight()*rateY);
jpDisplayImagen.getGraphics().drawImage(img, 0, 0,W,H, null);
}
else{
int W=(int)(img.getWidth()*rateX);
int H=(int)(img.getHeight()*rateX);
jpDisplayImagen.getGraphics().drawImage(img, 0, 0,W,H, null);
}
小开 
public class ImageTransformation {


public static final String PNG = "png";


public static byte[] resize(FileItem fileItem, int width, int height) {


try {
ResampleOp resampleOp = new ResampleOp(width, height);
BufferedImage scaledImage = resampleOp.filter(ImageIO.read(fileItem.getInputStream()), null);


ByteArrayOutputStream baos = new ByteArrayOutputStream();
ImageIO.write(scaledImage, PNG, baos);


return baos.toByteArray();
} catch (Exception ex) {
throw new MapsException("An error occured during image resizing.", ex);
}


}


public static byte[] resizeAdjustMax(FileItem fileItem, int maxWidth, int maxHeight) {


try {
BufferedInputStream bis = new BufferedInputStream(fileItem.getInputStream());
BufferedImage bufimg = ImageIO.read(bis);


//check size of image
int img_width = bufimg.getWidth();
int img_height = bufimg.getHeight();
if(img_width > maxWidth || img_height > maxHeight) {
float factx = (float) img_width / maxWidth;
float facty = (float) img_height / maxHeight;
float fact = (factx>facty) ? factx : facty;
img_width = (int) ((int) img_width / fact);
img_height = (int) ((int) img_height / fact);
}


return resize(fileItem,img_width, img_height);


} catch (Exception ex) {
throw new MapsException("An error occured during image resizing.", ex);
}


}

}

小开

Translated from here:

Dimension getScaledDimension(Dimension imageSize, Dimension boundary) {


double widthRatio = boundary.getWidth() / imageSize.getWidth();
double heightRatio = boundary.getHeight() / imageSize.getHeight();
double ratio = Math.min(widthRatio, heightRatio);


return new Dimension((int) (imageSize.width  * ratio),
(int) (imageSize.height * ratio));
}

You can also use imgscalr to resize images while maintaining aspect ratio:

BufferedImage resizeMe = ImageIO.read(new File("orig.jpg"));
Dimension newMaxSize = new Dimension(255, 255);
BufferedImage resizedImg = Scalr.resize(resizeMe, Method.QUALITY,
newMaxSize.width, newMaxSize.height);
小开

Just add one more block to Ozzy's code so the thing looks like this:

public static Dimension getScaledDimension(Dimension imgSize,Dimension boundary) {


int original_width = imgSize.width;
int original_height = imgSize.height;
int bound_width = boundary.width;
int bound_height = boundary.height;
int new_width = original_width;
int new_height = original_height;


// first check if we need to scale width
if (original_width > bound_width) {
//scale width to fit
new_width = bound_width;
//scale height to maintain aspect ratio
new_height = (new_width * original_height) / original_width;
}


// then check if we need to scale even with the new height
if (new_height > bound_height) {
//scale height to fit instead
new_height = bound_height;
//scale width to maintain aspect ratio
new_width = (new_height * original_width) / original_height;
}
// upscale if original is smaller
if (original_width < bound_width) {
//scale width to fit
new_width = bound_width;
//scale height to maintain aspect ratio
new_height = (new_width * original_height) / original_width;
}


return new Dimension(new_width, new_height);
}
小开

This is my solution:

/*
Change dimension of Image
*/
public static Image resizeImage(Image image, int scaledWidth, int scaledHeight, boolean preserveRatio) {


if (preserveRatio) {
double imageHeight = image.getHeight();
double imageWidth = image.getWidth();


if (imageHeight/scaledHeight > imageWidth/scaledWidth) {
scaledWidth = (int) (scaledHeight * imageWidth / imageHeight);
} else {
scaledHeight = (int) (scaledWidth * imageHeight / imageWidth);
}
}
BufferedImage inputBufImage = SwingFXUtils.fromFXImage(image, null);
// creates output image
BufferedImage outputBufImage = new BufferedImage(scaledWidth, scaledHeight, inputBufImage.getType());
// scales the input image to the output image
Graphics2D g2d = outputBufImage.createGraphics();
g2d.drawImage(inputBufImage, 0, 0, scaledWidth, scaledHeight, null);
g2d.dispose();
return SwingFXUtils.toFXImage(outputBufImage, null);
}
小开

All other answers show how to calculate the new image height in function of the new image width or vice-versa and how to resize the image using Java Image API. For those people who are looking for a straightforward solution I recommend any java image processing framework that can do this in a single line.

The exemple below uses Marvin Framework:

// 300 is the new width. The height is calculated to maintain aspect.
scale(image.clone(), image, 300);

Necessary import:

import static marvin.MarvinPluginCollection.*
小开

Load image:

BufferedImage bufferedImage = ImageIO.read(file);

Resize it:

private BufferedImage resizeAndCrop(BufferedImage bufferedImage, Integer width, Integer height) {


Mode mode = (double) width / (double) height >= (double) bufferedImage.getWidth() / (double) bufferedImage.getHeight() ? Scalr.Mode.FIT_TO_WIDTH
: Scalr.Mode.FIT_TO_HEIGHT;


bufferedImage = Scalr.resize(bufferedImage, Scalr.Method.ULTRA_QUALITY, mode, width, height);


int x = 0;
int y = 0;


if (mode == Scalr.Mode.FIT_TO_WIDTH) {
y = (bufferedImage.getHeight() - height) / 2;
} else if (mode == Scalr.Mode.FIT_TO_HEIGHT) {
x = (bufferedImage.getWidth() - width) / 2;
}


bufferedImage = Scalr.crop(bufferedImage, x, y, width, height);


return bufferedImage;
}

Using Scalr library:

<dependency>
<groupId>org.imgscalr</groupId>
<artifactId>imgscalr-lib</artifactId>
<version>4.2</version>
</dependency>
小开

I have found the selected answer to have problems with upscaling, and so I have made (yet) another version (which I have tested):

public static Point scaleFit(Point src, Point bounds) {
int newWidth = src.x;
int newHeight = src.y;
double boundsAspectRatio = bounds.y / (double) bounds.x;
double srcAspectRatio = src.y / (double) src.x;


// first check if we need to scale width
if (boundsAspectRatio < srcAspectRatio) {
// scale width to fit
newWidth = bounds.x;
//scale height to maintain aspect ratio
newHeight = (newWidth * src.y) / src.x;
} else {
//scale height to fit instead
newHeight = bounds.y;
//scale width to maintain aspect ratio
newWidth = (newHeight * src.x) / src.y;
}


return new Point(newWidth, newHeight);
}

Written in Android terminology :-)

as for the tests:

@Test public void scaleFit() throws Exception {
final Point displaySize = new Point(1080, 1920);
assertEquals(displaySize, Util.scaleFit(displaySize, displaySize));
assertEquals(displaySize, Util.scaleFit(new Point(displaySize.x / 2, displaySize.y / 2), displaySize));
assertEquals(displaySize, Util.scaleFit(new Point(displaySize.x * 2, displaySize.y * 2), displaySize));
assertEquals(new Point(displaySize.x, displaySize.y * 2), Util.scaleFit(new Point(displaySize.x / 2, displaySize.y), displaySize));
assertEquals(new Point(displaySize.x * 2, displaySize.y), Util.scaleFit(new Point(displaySize.x, displaySize.y / 2), displaySize));
assertEquals(new Point(displaySize.x, displaySize.y * 3 / 2), Util.scaleFit(new Point(displaySize.x / 3, displaySize.y / 2), displaySize));
}
小开

Here's a small piece of code that I wrote, it resizes the image to fit the container while keeping the image's original aspect ratio. It takes in as parameters the container's width, height and the image. You can modify it to fit your needs. It's simple and works fine for my applications.

private Image scaleimage(int wid, int hei, BufferedImage img){
Image im = img;
double scale;
double imw = img.getWidth();
double imh = img.getHeight();
if (wid > imw && hei > imh){
im = img;
}else if(wid/imw < hei/imh){
scale = wid/imw;
im = img.getScaledInstance((int) (scale*imw), (int) (scale*imh), Image.SCALE_SMOOTH);
}else if (wid/imw > hei/imh){
scale = hei/imh;
im = img.getScaledInstance((int) (scale*imw), (int) (scale*imh), Image.SCALE_SMOOTH);
}else if (wid/imw == hei/imh){
scale = wid/imw;
im = img.getScaledInstance((int) (scale*imw), (int) (scale*imh), Image.SCALE_SMOOTH);
}
return im;
}

提交答案