C：TIFFWriteEncodedStrip 与 Java：？

Question

在 Java 中，在创建使用 TIFFFields 配置的关联 TIFFDirectory 后，如何使用 TIFFImageWriter 将相同的字节数组写入 tiff 文件

还没有看到任何 Java 相似之处。

更多信息

压缩：T4_COMPRESSION_T4_1D

在https://github.com/freeswitch/spandsp/blob/master/src/t4_t6_decode.c

压缩传真图像的每行：

/* 将游程转换为行的位图 */

/* White/black/white... runs, always starting with white. 
    That means the first run could be zero length. */

        for (x = 0, fudge = 0;  x < s->a_cursor;  x++, fudge ^= 0xFF)
        {
            i = s->cur_runs[x];
            if ((int) i >= s->pixels)
            {
                s->pixel_stream = (s->pixel_stream << s->pixels) |
                                  (msbmask[s->pixels] & fudge);
                for (i += (8 - s->pixels);  i >= 8;  i -= 8)
                {
                    s->pixels = 8;
                    s->row_buf[row_pos++] = (uint8_t) s->pixel_stream;
                    s->pixel_stream = fudge;
                }
            }
            s->pixel_stream = (s->pixel_stream << i) | (msbmask[i] & fudge);
            s->pixels -= i;
        }
        s->image_length++;
    

每个 row_buf 字节都会累积在一页的 image_buffer 中， 在 t4_rx.c write_tiff_image(t4_rx_state_t *s) 中，条带 通过以下方式写入文件：

 /* Let libtiff do the compression */
 TIFFWriteEncodedStrip(t->tiff_file, 0, t->image_buffer, t->image_size)
    

问：要在java中执行此操作，包含页面的字节数组如何 像素/位传递给 TiffImageWriter 对象？

Answer 1

我不完全确定我理解你的问题，但你的字节数组似乎包含打包成字节的 1 位像素信息。

您可以基于这些字节创建 BufferedImage，然后使用 ImageIO 将其写入 TIFF。

首先，根据数据制作 BufferedImage：

• 将字节数组包装在 DataBufferByte
中
• 创建一个 Raster，指定它将缓冲区的字节视为打包到字节中的 1 位像素。
• 创建一个 ColorModel 指示如何写入 1 位像素。
• 最后，从该 Raster 和 ColorModel 创建一个 BufferedImage。

DataBuffer buffer = new DataBufferByte(pixels, pixels.length);
WritableRaster raster =
    Raster.createPackedRaster(buffer, imageWidth, imageHeight, 1, null);

byte[] colors = { 0x00, (byte) 0xff };  // 0=black, 1=white
ColorModel colorModel =
    new IndexColorModel(1, colors.length, colors, colors, colors);

BufferedImage image =
    new BufferedImage(colorModel, raster, false, new Properties());

ImageIO TIFF 元数据规范描述了如何指定 TIFF 压缩：

ImageWriter tiffWriter =
    ImageIO.getImageWritersByFormatName("TIFF").next();

ImageWriteParam param = tiffWriter.getDefaultWriteParam();

param.setCompressionMode(ImageWriteParam.MODE_EXPLICIT);
param.setCompressionType("CCITT T.4");

IIOImage iioImage = new IIOImage(image, null, null);

try (ImageOutputStream out = ImageIO.createImageOutputStream(
    new BufferedOutputStream(
        Files.newOutputStream(filename)))) {

    tiffWriter.setOutput(out);
    tiffWriter.write(null, iioImage, param);
} finally {
    tiffWriter.dispose();
}

完整方法如下：

public void writeTIFF(byte[] pixels,
                      int imageWidth,
                      int imageHeight,
                      Path filename)
throws IOException {
    DataBuffer buffer = new DataBufferByte(pixels, pixels.length);
    WritableRaster raster =
        Raster.createPackedRaster(buffer, imageWidth, imageHeight, 1, null);

    byte[] colors = { 0x00, (byte) 0xff };  // 0=black, 1=white
    ColorModel colorModel =
        new IndexColorModel(1, colors.length, colors, colors, colors);

    BufferedImage image =
        new BufferedImage(colorModel, raster, false, new Properties());

    ImageWriter tiffWriter =
        ImageIO.getImageWritersByFormatName("TIFF").next();

    ImageWriteParam param = tiffWriter.getDefaultWriteParam();

    param.setCompressionMode(ImageWriteParam.MODE_EXPLICIT);
    param.setCompressionType("CCITT T.4");

    IIOImage iioImage = new IIOImage(image, null, null);

    try (ImageOutputStream out = ImageIO.createImageOutputStream(
        new BufferedOutputStream(
            Files.newOutputStream(filename)))) {

        tiffWriter.setOutput(out);
        tiffWriter.write(null, iioImage, param);
    } finally {
        tiffWriter.dispose();
    }
}