如何从Java保存带有tEXt或iTXt块的PNG？

png text java javax.imageio

2022-09-04 21:34:12

我目前正在使用javax.imageio.ImageIO来编写PNG文件。我想包括一个tEXt块（以及这里列出的任何块），但看不到这样做的方法。

从com.sun.imageio.plugins.png.PNGMetadata来看，这应该是可能的。

我应该非常感谢任何线索或答案。

M.

答案 1

我在一些反编译后找到的解决方案如下...

RenderedImage image = getMyImage();         
Iterator<ImageWriter> iterator = ImageIO.getImageWritersBySuffix( "png" );

if(!iterator.hasNext()) throw new Error( "No image writer for PNG" );

ImageWriter imagewriter = iterator.next();
ByteArrayOutputStream bytes = new ByteArrayOutputStream();
imagewriter.setOutput( ImageIO.createImageOutputStream( bytes ) ); 

// Create & populate metadata
PNGMetadata metadata = new PNGMetadata();
// see http://www.w3.org/TR/PNG-Chunks.html#C.tEXt for standardized keywords
metadata.tEXt_keyword.add( "Title" );
metadata.tEXt_text.add( "Mandelbrot" );
metadata.tEXt_keyword.add( "Comment" );
metadata.tEXt_text.add( "..." );
metadata.tEXt_keyword.add( "MandelbrotCoords" ); // custom keyword
metadata.tEXt_text.add( fractal.getCoords().toString() );           

// Render the PNG to memory
IIOImage iioImage = new IIOImage( image, null, null );
iioImage.setMetadata( metadata ); // Attach the metadata
imagewriter.write( null, iioImage, null );

答案 2

我意识到这个问题早就得到了答案，但是如果你想在不陷入“com.sun”层次结构的情况下做到这一点，这里有一个快速且非常丑陋的例子，因为我在其他任何地方都找不到这个记录。

BufferedImage img = new BufferedImage(300, 300, BufferedImage.TYPE_INT_ARGB);

// Create a DOM Document describing the metadata;
// I've gone the quick and dirty route. The description for PNG is at
// [http://download.oracle.com/javase/1.4.2/docs/api/javax/imageio/metadata/doc-files/png_metadata.html][1]

Calendar c = Calendar.getInstance();
String xml = "<?xml version='1.0'?><javax_imageio_png_1.0><tIME year='"+c.get(c.YEAR)+"' month='"+(c.get(c.MONTH)+1)+"' day='"+c.get(c.DAY_OF_MONTH)+"' hour='"+c.get(c.HOUR_OF_DAY)+"' minute='"+c.get(c.MINUTE)+"' second='"+c.get(c.SECOND)+"'/><pHYs pixelsPerUnitXAxis='"+11811+"' pixelsPerUnitYAxis='"+11811+"' unitSpecifier='meter'/></javax_imageio_png_1.0>";
DOMResult domresult = new DOMResult();
TransformerFactory.newInstance().newTransformer().transform(new StreamSource(new StringReader(xml)), domresult);
Document document = dom.getResult();

// Apply the metadata to the image
ImageWriter writer = (ImageWriter)ImageIO.getImageWritersBySuffix("png").next();
IIOMetadata meta = writer.getDefaultImageMetadata(new ImageTypeSpecifier(img), null);
meta.setFromTree(meta.getMetadataFormatNames()[0], document.getFirstChild());
FileOutputStream out = new FileOutputStream("out.png");
writer.setOutput(ImageIO.createImageOutputStream(out));
writer.write(new IIOImage(img, null, meta));
out.close();