用libtiff如何将cmyk四张分色图合并成一张tiff？

以下是使用libtiff将CMYK四张分色图合并成一张TIFF的步骤：

1. 打开每个CMYK分色图并读取它们的图像数据。您可以使用libtiff的TIFFOpen和TIFFReadRGBAImage函数来实现。

2. 创建一个新的TIFF文件并使用libtiff的TIFFSetField函数设置必要的标签，如图像宽度、高度、位深度和颜色模式。对于CMYK图像，您需要设置TIFFTAG_PHOTOMETRIC标签为PHOTOMETRIC_SEPARATED，TIFFTAG_INKSET标签为INKSET_CMYK和TIFFTAG_SAMPLESPERPIXEL标签为4。

3. 将CMYK分色图的数据写入新的TIFF文件。您可以使用libtiff的TIFFWriteScanline函数将每个分色图的扫描线写入新的TIFF文件。

4. 关闭所有文件并释放所有资源。

以下是一个示例代码，它将四张CMYK分色图合并成一张TIFF：

#include <stdio.h>
#include <stdlib.h>
#include <tiffio.h>

int main()
{
    // Open the four CMYK separation files
    TIFF* cyan = TIFFOpen("cyan.tif", "r");
    TIFF* magenta = TIFFOpen("magenta.tif", "r");
    TIFF* yellow = TIFFOpen("yellow.tif", "r");
    TIFF* black = TIFFOpen("black.tif", "r");
    
    // Read image data from each file
    uint32 width, height;
    TIFFGetField(cyan, TIFFTAG_IMAGEWIDTH, &width);
    TIFFGetField(cyan, TIFFTAG_IMAGELENGTH, &height);
    uint32* cdata = (uint32*)malloc(width * height * sizeof(uint32));
    TIFFReadRGBAImage(cyan, width, height, cdata, 0);
    uint32* mdata = (uint32*)malloc(width * height * sizeof(uint32));
    TIFFReadRGBAImage(magenta, width, height, mdata, 0);
    uint32* ydata = (uint32*)malloc(width * height * sizeof(uint32));
    TIFFReadRGBAImage(yellow, width, height, ydata, 0);
    uint32* kdata = (uint32*)malloc(width * height * sizeof(uint32));
    TIFFReadRGBAImage(black, width, height, kdata, 0);
    
    // Create a new TIFF file and set necessary tags
    TIFF* output = TIFFOpen("output.tif", "w");
    TIFFSetField(output, TIFFTAG_IMAGEWIDTH, width);
    TIFFSetField(output, TIFFTAG_IMAGELENGTH, height);
    TIFFSetField(output, TIFFTAG_BITSPERSAMPLE, 8);
    TIFFSetField(output, TIFFTAG_PHOTOMETRIC, PHOTOMETRIC_SEPARATED);
    TIFFSetField(output, TIFFTAG_INKSET, INKSET_CMYK);
    TIFFSetField(output, TIFFTAG_SAMPLESPERPIXEL, 4);
    
    // Write image data to the new TIFF file
    for (uint32 row = 0; row < height; row++)
    {
        uint32* scanline = (uint32*)malloc(width * sizeof(uint32));
        for (uint32 col = 0; col < width; col++)
        {
            uint32 c = (cdata[row * width + col] >> 24) & 0xff;
            uint32 m = (mdata[row * width + col] >> 24) & 0xff;
            uint32 y = (ydata[row * width + col] >> 24) & 0xff;
            uint32 k = (kdata[row * width + col] >> 24) & 0xff;
            scanline[col] = (k << 24) | (y << 16) | (m << 8) | c;
        }
        TIFFWriteScanline(output, scanline, row);
        free(scanline);
    }
    
    // Close all files and free all resources
    TIFFClose(cyan);
    TIFFClose(magenta);
    TIFFClose(yellow);
    TIFFClose(black);
    TIFFClose(output);
    free(cdata);
    free(mdata);
    free(ydata);
    free(kdata);
    
    return 0;
}