在 Batik 中使用 SVGConverter 将 svg 转换为 png 时图像质量不佳

Question

我转换后的图像质量非常低。 我曾尝试使用 setQuality 方法，但它似乎没有改变任何东西。

这是将 svg 转换为 png 的代码部分：

SVGConverter svgConverter = new SVGConverter();
String[] sources = { "C:/imageData.svg" };
svgConverter.setSources(sources);
svgConverter.setDestinationType(DestinationType.PNG);
svgConverter.setDst(new File("C:/image.png"));

有谁知道我怎样才能使图像质量更好？

Answer 1

我在将 SVG 转换为 PNG 时使用此代码（使用字节数组）：

private byte[] renderPng(byte[] svgBytes) {
    try {
        TranscoderInput transcoderInput = new TranscoderInput(new ByteArrayInputStream(svgBytes));
        ByteArrayOutputStream output = new ByteArrayOutputStream();
        TranscoderOutput transcoderOutput = new TranscoderOutput(output);

        Transcoder transcoder = null;
        String type = "png";
        if(type.equalsIgnoreCase("png")) { 
            transcoder = new PNGTranscoder()
            {
                @Override
                protected ImageRenderer createRenderer()
                {
                    ImageRenderer r = super.createRenderer();

                    RenderingHints rh = r.getRenderingHints();

                    rh.add(new RenderingHints(RenderingHints.KEY_ALPHA_INTERPOLATION,
                        RenderingHints.VALUE_ALPHA_INTERPOLATION_QUALITY));
                    rh.add(new RenderingHints(RenderingHints.KEY_INTERPOLATION,
                        RenderingHints.VALUE_INTERPOLATION_BICUBIC));

                    rh.add(new RenderingHints(RenderingHints.KEY_ANTIALIASING,
                        RenderingHints.VALUE_ANTIALIAS_ON));

                    rh.add(new RenderingHints(RenderingHints.KEY_COLOR_RENDERING,
                        RenderingHints.VALUE_COLOR_RENDER_QUALITY));
                    rh.add(new RenderingHints(RenderingHints.KEY_DITHERING,
                        RenderingHints.VALUE_DITHER_DISABLE));

                    rh.add(new RenderingHints(RenderingHints.KEY_RENDERING,
                        RenderingHints.VALUE_RENDER_QUALITY));

                    rh.add(new RenderingHints(RenderingHints.KEY_STROKE_CONTROL,
                        RenderingHints.VALUE_STROKE_PURE));

                    rh.add(new RenderingHints(RenderingHints.KEY_FRACTIONALMETRICS,
                        RenderingHints.VALUE_FRACTIONALMETRICS_ON));
                    rh.add(new RenderingHints(RenderingHints.KEY_TEXT_ANTIALIASING,
                        RenderingHints.VALUE_TEXT_ANTIALIAS_OFF));

                    r.setRenderingHints(rh);

                    return r;
                }
            };

            transcoder.addTranscodingHint(PNGTranscoder.KEY_BACKGROUND_COLOR, Color.WHITE);
        } else {
            transcoder = new JPEGTranscoder();

            Float jpegQuality = new Float(0.95);
            // KEY_WIDTH - seems to pick it up just fine from the SVG charts.  Set to 560 otherwise.
            // KEY_QUALITY 0-1.0 with 1.0 being No Loss.  Value must be of type Float.  0.95 is 30% smaller and looks great.
            transcoder.addTranscodingHint(JPEGTranscoder.KEY_QUALITY, jpegQuality);
        }

        // NOTE: for linux you need Java 1.4.1+ AND the headless environment (e.g. export JAVA_OPTS='-Djava.awt.headless=true').
        try {
            transcoder.transcode(transcoderInput, transcoderOutput);
        }
        catch(Exception e) {
            logger.error("SVG To Raster response transcode exception", e);
            if(output != null) {
                output.close();
            }
            throw( new RuntimeException("SVG To Raster Filter Response Stream Exception", e) );
        }

        if(output != null) {
            output.flush();
            output.close();
        }

        transcoderInput  = null;
        transcoderOutput = null;
        transcoder = null;

        return output.toByteArray();
    } catch (Exception exc) {
        logger.error("Error in rendering png method", exc);
    }
    return new byte[0];
}

此外，SVG 文档中的 clipPath 元素应包含此属性，否则会出现奇怪的工件：

<clipPath shape-rendering="geometricPrecision" ... >

Answer 2

在 Apache Batik 中，您可以通过传递转码器提示 KEY_PIXEL_UNIT_TO_MILLIMETER 来更改分辨率。

然而，重要的方面是您需要将高度和宽度缩放到与您正在寻求的新分辨率相同的比例。

例如：

我的 SVG 有 3.5 * 2.0 英寸（252 * 144 像素）大小。

目标分辨率为 600 DPI。

int RESOLUTION_DPI = 600;
float SCALE_BY_RESOLUTION = RESOLUTION_DPI / 72f;
float scaledWidth = 252*SCALE_BY_RESOLUTION;
float scaledHeight = 144*SCALE_BY_RESOLUTION;
float pixelUnitToMM = new Float(25.4f/RESOLUTION_DPI);

transcoderInput = new TranscoderInput(svgDocument);
TranscoderOutput transcoderOutput = new TranscoderOutput(ostream);
transcoder.addTranscodingHint(ImageTranscoder.KEY_BACKGROUND_COLOR, Color.WHITE);
transcoder.addTranscodingHint(PNGTranscoder.KEY_WIDTH, scaledWidth);
transcoder.addTranscodingHint(PNGTranscoder.KEY_HEIGHT, scaledHeight);

transcoder.addTranscodingHint(PNGTranscoder.KEY_PIXEL_UNIT_TO_MILLIMETER, pixelUnitToMM);

transcoder.transcode(transcoderInput, transcoderOutput);

Answer 3

尝试这个....

jpeg.addTranscodingHint(JPEGTranscoder.KEY_QUALITY, new Float(keyQuality));
jpeg.addTranscodingHint(JPEGTranscoder.KEY_HEIGHT, height*scalePercentage);
jpeg.addTranscodingHint(JPEGTranscoder.KEY_WIDTH, width*scalePercentage);
jpeg.addTranscodingHint(JPEGTranscoder.KEY_QUALITY, 1.0f);
jpeg.addTranscodingHint(JPEGTranscoder.KEY_BACKGROUND_COLOR, Color.WHITE);

您需要像 set keyQuality 1.0f 一样增加高度和宽度。

如果 height=200 将高度增加 200*3(height*scalePercentage)。 宽度也类似