调整大小后的图像质量非常低-- Java
调整大小后的图像质量非常低-- Java
提问于 2013-01-02 09:32:01
在脚本中，它从300x300左右下降到60x60。需要提高整体图像质量，因为它是出来非常糟糕的时刻。
public static Boolean resizeImage(String sourceImg, String destImg, Integer Width, Integer Height, Integer whiteSpaceAmount)
{
BufferedImage origImage;
try
{
origImage = ImageIO.read(new File(sourceImg));
int type = origImage.getType() == 0? BufferedImage.TYPE_INT_ARGB : origImage.getType();
int fHeight = Height;
int fWidth = Width;
int whiteSpace = Height + whiteSpaceAmount; //Formatting all to squares so don't need two whiteSpace calcs..
double aspectRatio;
//Work out the resized dimensions
if (origImage.getHeight() > origImage.getWidth()) //If the pictures height is greater than the width then scale appropriately.
{
fHeight = Height; //Set the height to 60 as it is the biggest side.
aspectRatio = (double)origImage.getWidth() / (double)origImage.getHeight(); //Get the aspect ratio of the picture.
fWidth = (int)Math.round(Width * aspectRatio); //Sets the width as created via the aspect ratio.
}
else if (origImage.getHeight() < origImage.getWidth()) //If the pictures width is greater than the height scale appropriately.
{
fWidth = Width; //Set the height to 60 as it is the biggest side.
aspectRatio = (double)origImage.getHeight() / (double)origImage.getWidth(); //Get the aspect ratio of the picture.
fHeight = (int)Math.round(Height * aspectRatio); //Sets the height as created via the aspect ratio.
}
int extraHeight = whiteSpace - fHeight;
int extraWidth = whiteSpace - fWidth;
BufferedImage resizedImage = new BufferedImage(whiteSpace, whiteSpace, type);
Graphics2D g = resizedImage.createGraphics();
g.setColor(Color.white);
g.fillRect(0, 0, whiteSpace, whiteSpace);
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);
g.drawImage(origImage, extraWidth/2, extraHeight/2, fWidth, fHeight, null);
g.dispose();
ImageIO.write(resizedImage, "jpg", new File(destImg));
}
catch (IOException ex)
{
return false;
}
return true;
}真的只需要知道他们是我可以插入的东西，将提高质量，或者如果我需要看一些完全不同的东西。
编辑:图片对比。
消息来源，刚刚从谷歌随机挑选了一台洗衣机。http://www.essexappliances.co.uk/images/categories/washing-machine.jpg
同样的图片在Photoshop中转换成我需要的样子。http://imgur.com/78B1p
它看起来像这样被转换了。http://imgur.com/8WlXD
回答 4
Stack Overflow用户
回答已采纳
发布于 2013-01-02 12:40:18
您看到的问题实际上与用于缩小比例的重采样滤波器有关。显然，您的库使用的是一个不适合这种情况的库。最近邻，双线性和双三次是典型的不好的例子，在缩小尺度时使用。我不知道Photoshop使用的确切重采样滤镜，但我使用了3叶lanczos，得到了以下结果：
因此，要解决您的问题，需要使用更智能的重采样过滤器。
Stack Overflow用户
发布于 2013-01-02 12:07:00
在很大的范围内缩小图像是固有的危险(从质量的角度来看)，特别是使用单个步骤。
推荐的方法是使用分而治之的方法。基本上，您可以按50%的步长缩小图像，直到达到所需的大小。
因此，我取了650x748的原始图像，并将其缩小到60x60区域(52x60)。
分而治之只需一步...
public class TestImageResize {
public static void main(String[] args) {
new TestImageResize();
}
public TestImageResize() {
EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (Exception ex) {
}
JFrame frame = new JFrame("Testing");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLayout(new BorderLayout());
frame.add(new ScalePane());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public class ScalePane extends JPanel {
private BufferedImage original;
private BufferedImage scaled;
public ScalePane() {
try {
original = ImageIO.read(new File("path/to/master.jpg"));
scaled = getScaledInstanceToFit(original, new Dimension(60, 60));
ImageIO.write(scaled, "jpg", new File("scaled.jpg"));
BufferedImage image = new BufferedImage(52, 60, BufferedImage.TYPE_INT_RGB);
Graphics2D g2d = image.createGraphics();
g2d.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BILINEAR);
g2d.setRenderingHint(RenderingHints.KEY_RENDERING, RenderingHints.VALUE_RENDER_QUALITY);
g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
g2d.drawImage(original, 0, 0, 52, 60, this);
g2d.dispose();
ImageIO.write(image, "jpg", new File("test.jpg"));
} catch (IOException ex) {
ex.printStackTrace();
}
}
@Override
public Dimension getPreferredSize() {
Dimension size = super.getPreferredSize();
if (original != null) {
if (scaled != null) {
size.width = original.getWidth() + scaled.getWidth();
size.height = original.getHeight();
} else {
size.width = original.getWidth();
size.height = original.getHeight();
}
}
return size;
}
@Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g.create();
g2d.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BILINEAR);
g2d.setRenderingHint(RenderingHints.KEY_RENDERING, RenderingHints.VALUE_RENDER_QUALITY);
g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
if (original != null) {
int x = 0;
int y = (getHeight() - original.getHeight()) / 2;;
if (scaled != null) {
x = (getWidth() - (original.getWidth() + scaled.getWidth())) / 2;
} else {
x = (getWidth() - original.getWidth()) / 2;
}
g2d.drawImage(original, x, y, this);
if (scaled != null) {
x += original.getWidth();
y = (getHeight() - scaled.getHeight()) / 2;
g2d.drawImage(scaled, x, y, this);
}
}
g2d.dispose();
}
public BufferedImage getScaledInstanceToFit(BufferedImage img, Dimension size) {
float scaleFactor = getScaleFactorToFit(img, size);
return getScaledInstance(img, scaleFactor);
}
public float getScaleFactorToFit(BufferedImage img, Dimension size) {
float scale = 1f;
if (img != null) {
int imageWidth = img.getWidth();
int imageHeight = img.getHeight();
scale = getScaleFactorToFit(new Dimension(imageWidth, imageHeight), size);
}
return scale;
}
public float getScaleFactorToFit(Dimension original, Dimension toFit) {
float scale = 1f;
if (original != null && toFit != null) {
float dScaleWidth = getScaleFactor(original.width, toFit.width);
float dScaleHeight = getScaleFactor(original.height, toFit.height);
scale = Math.min(dScaleHeight, dScaleWidth);
}
return scale;
}
public float getScaleFactor(int iMasterSize, int iTargetSize) {
float scale = 1;
if (iMasterSize > iTargetSize) {
scale = (float) iTargetSize / (float) iMasterSize;
} else {
scale = (float) iTargetSize / (float) iMasterSize;
}
return scale;
}
public BufferedImage getScaledInstance(BufferedImage img, double dScaleFactor) {
BufferedImage imgBuffer = null;
imgBuffer = getScaledInstance(img, dScaleFactor, RenderingHints.VALUE_INTERPOLATION_BILINEAR, true);
return imgBuffer;
}
protected BufferedImage getScaledInstance(BufferedImage img, double dScaleFactor, Object hint, boolean higherQuality) {
int targetWidth = (int) Math.round(img.getWidth() * dScaleFactor);
int targetHeight = (int) Math.round(img.getHeight() * dScaleFactor);
int type = (img.getTransparency() == Transparency.OPAQUE)
? BufferedImage.TYPE_INT_RGB : BufferedImage.TYPE_INT_ARGB;
BufferedImage ret = (BufferedImage) img;
if (targetHeight > 0 || targetWidth > 0) {
int w, h;
if (higherQuality) {
w = img.getWidth();
h = img.getHeight();
} else {
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(Math.max(w, 1), Math.max(h, 1), 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);
} else {
ret = new BufferedImage(1, 1, type);
}
return ret;
}
}
}您还可以找到感兴趣的The Perils of Image.getScaledInstance()。
Stack Overflow用户
发布于 2013-01-02 23:59:29
荷兰人，这就是我维护imgscalr library的原因--让这类事情变得非常简单。
在您的示例中，紧跟在第一个ImageIO.read行之后，一个方法调用就可以完成此任务：
origImage = ImageIO.read(new File(sourceImg));您可以执行以下操作来获取所需内容(javadoc for this method)：
origImage = Scalr.resize(origImage, Method.ULTRA_QUALITY, 60);如果仍然看起来有点锯齿(因为您要从图像中删除太多信息，您可以将以下操作添加到命令中，以便对图像应用轻型抗锯齿滤镜，使其看起来更平滑)：
origImage = Scalr.resize(origImage, Method.ULTRA_QUALITY, 60, Scalr.OP_ANTIALIAS);这将替换您拥有的所有剩余的代码逻辑。我唯一推荐的另一件事是将你非常小的样本保存为PNG，这样就不会在图像上进行更多的压缩/有损转换，或者如果你真的想要JPG格式，请确保你对JPG使用很少甚至没有压缩。(这里是关于如何做的an article；它利用了ImageWriteParam类)
imgscalr是在Apache2许可下授权的，托管在GitHub上，所以你可以随心所欲地使用它；如果你在服务器端应用程序中使用该库，并在大量伸缩操作中排队，并且不想杀死服务器，它还包括asynchronous scaling support。
页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/14115950
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