使用BufferedImage生成缩略图,而无需反转颜色并在Java中获得alpha

时间:2019-02-27 05:28:56

标签: java graphics

我使用“ BufferedImage”通过此代码生成缩略图。

try {
 BufferedImage bi = new BufferedImage(thumWidth, thumHeight, TYPE_INT_ARGB);
 Graphics2D g = bi.createGraphics();

 Image ii = (new ImageIcon(orgFile.getAbsolutePath())).getImage();

 g.drawImage(ii, 0, 0, thumWidth, thumHeight, null);
 String thumbFileDir = prefixPath + "/" + thumWidth + "/" + afterPath;
 File file = this.createPathIfnotexist(thumbFileDir);
 String fullPathToSave = this.genPath(file.getAbsolutePath(), fileName);
 File thumbFile = new File(fullPathToSave);
 ImageIO.write(bi, ext, thumbFile);
} catch (IOException var22) {
 var22.printStackTrace();
 return;
} catch (Exception var23) {
 var23.printStackTrace();
}

我的问题是...

  1. 当我使用TYPE_INT_RGB获取BufferedImage实例时,发送PNG文件时丢失alpha,发送JPG文件时也可以。 OriginalConverted

  2. 当我使用TYPE_INT_ARGB获取BufferedImage实例时,在发送PNG文件时获得alpha,但是在发送JPG文件时颜色却相反。 OriginalConverted

因此,我想创建缩略图而不反转颜色并保持alpha。我该怎么办?

1 个答案:

答案 0 :(得分:0)

作为我不断研究的结果,我认为使用外部库比以问题中建议的方式进行尝试更方便。

因此,我决定使用java-image-scaling生成缩略图。

对于那些将来访问此页面的人,我留下一些代码。 (实际上,问题是用Java编写的,而答案是用Kotlin编写的。)

imgLocation是原始图像的上传路径,width是参考点,例如100、240、480、720、1080。

    private val rootLocation: Path by lazy { Paths.get(location) }
    private val formatNames = ImageIO.getWriterFormatNames().toList()

    override fun resizeImage(imgLocation: String, width: Int): File {
        val originFile = this.rootLocation.resolve(imgLocation).toFile()
        val destFile = this.rootLocation.resolve("resized-$width-${originFile.name}").toFile()

        val bufferedImage: BufferedImage = originFile.inputStream().use { ImageIO.read(it) }
        val resizeImage = if (width <= bufferedImage.width) {
            val nHeight = width * bufferedImage.height / bufferedImage.width
            val rescale = MultiStepRescaleOp(width, nHeight).apply { unsharpenMask = AdvancedResizeOp.UnsharpenMask.Soft }
            rescale.filter(bufferedImage, null)
        } else {
            bufferedImage
        }

        val target = if (formatNames.contains(destFile.extension)) destFile else File(destFile.path + ".jpg")
        ImageIO.write(resizeImage, target.extension, target)

        bufferedImage.flush()
        return destFile
    }