ras2tiff Command in Linux

The ras2tiff command in Linux is used to convert Sun rasterfiles to TIFF (Tagged Image File Format) files. This command is part of the libtiff library and utilities, which are used for manipulating TIFF images. The ras2tiff command is particularly useful for converting raster images to the more widely supported TIFF format.

Table of Contents

Here is a comprehensive guide to the options available with the ras2tiff command −

• Understanding of ras2tiff Command
• Syntax of ras2tiff Command
• ras2tiff Command Options
• Examples of ras2tiff Command in Linux
• Samples per Pixel
• Bits per Sample

Understanding of ras2tiff Command

The ras2tiff command in Linux is used to convert Sun rasterfiles into TIFF files. By default, the TIFF image is created with data samples packed, compressed using the Lempel-Ziv & Welch algorithm, and with each strip no more than 8 kilobytes in size. The command also carries over any colormap information from the rasterfile to the TIFF file, setting the appropriate Photometric Interpretation tag based on the image depth. Users can specify different compression schemes and the number of rows per strip using various options.

Understanding TIFF Files

TIFF (Tagged Image File Format) is a flexible and widely supported image format used for storing raster graphics. TIFF files can store images with various bit depths and compression schemes, making them suitable for a wide range of applications, including document scanning, digital photography, and medical imaging.

Compression Schemes

The ras2tiff command supports several compression schemes for the output TIFF file −

• none − No compression.
• packbits − A simple run-length encoding scheme.
• lzw − Lempel-Ziv-Welch compression, a lossless data compression algorithm.
• jpeg − JPEG compression, a lossy compression algorithm commonly used for photographic images.
• deflate − A lossless data compression algorithm similar to that used in the ZIP file format.

Photometric Interpretations

The ras2tiff command supports several photometric interpretations for the output TIFF file −

• miniswhite − Pixel values of 0 represent white, and maximum pixel values represent black.
• minisblack − Pixel values of 0 represent black, and maximum pixel values represent white.
• rgb − Pixel values represent red, green, and blue colour channels.

Syntax of ras2tiff Command

The basic syntax of the ras2tiff command is as follows −

ras2tiff [options] input.ras output.tiff

• input.ras − The name of the input Sun rasterfile.
• output.tiff − The name of the output TIFF file.

ras2tiff Command Options

Examples of ras2tiff Command in Linux

Sun rasterfiles are a bitmap image format used primarily on Sun Microsystems workstations. They can store images with various bit depths, including 1-bit monochrome, 8-bit grayscale, and 24-bit color.

• Converting a Sun Rasterfile to a TIFF File
• Specifying Compression for the Output TIFF File
• Setting the Resolution of the Output TIFF File
• Setting the Photometric Interpretation of the Output TIFF File
• Setting the Number of Samples per Pixel in the Output TIFF File
• Setting the Number of Bits per Sample in the Output TIFF File

Converting a Sun Rasterfile to a TIFF File

To convert a Sun rasterfile to a TIFF file, you can use the following command −

ras2tiff input.ras output.tiff

For example, if you have a Sun rasterfile named image.ras and you want to convert it to a TIFF file named image.tiff, you would use −

ras2tiff image.ras image.tiff

Specifying Compression for the Output TIFF File

To specify the compression scheme for the output TIFF file, you can use the -c option −

ras2tiff -c lzw input.ras output.tiff

For example, to convert a Sun rasterfile named image.ras to a TIFF file named image.tiff with LZW compression, you would use −

ras2tiff -c lzw image.ras image.tiff

Setting the Resolution of the Output TIFF File

To set the resolution of the output TIFF file, you can use the -r option −

ras2tiff -r 300 input.ras output.tiff

For example, to convert a Sun rasterfile named image.ras to a TIFF file named image.tiff with a resolution of 300 DPI, you would use −

ras2tiff -r 300 image.ras image.tiff

Setting the Photometric Interpretation of the Output TIFF File

To set the photometric interpretation of the output TIFF file, you can use the -p option −

ras2tiff -p rgb input.ras output.tiff

For example, to convert a Sun rasterfile named image.ras to a TIFF file named image.tiff with RGB photometric interpretation, you would use −

ras2tiff -p rgb image.ras image.tiff

Setting the Number of Samples per Pixel in the Output TIFF File

To set the number of samples per pixel in the output TIFF file, you can use the -s option −

ras2tiff -s 3 input.ras output.tiff

For example, to convert a Sun rasterfile named image.ras to a TIFF file named image.tiff with 3 samples per pixel, you would use −

ras2tiff -s 3 image.ras image.tiff

Setting the Number of Bits per Sample in the Output TIFF File

To set the number of bits per sample in the output TIFF file, you can use the -b option −

ras2tiff -b 8 input.ras output.tiff

For example, to convert a Sun rasterfile named image.ras to a TIFF file named image.tiff with 8 bits per sample, you would use −

ras2tiff -b 8 image.ras image.tiff

Samples per Pixel

The number of samples per pixel specifies how many color channels are present in the image. For example, an RGB image has 3 samples per pixel (one for each color channel), while a grayscale image has 1 sample per pixel.

Bits per Sample

The number of bits per sample specifies the bit depth of each color channel. For example, an 8-bit grayscale image has 8 bits per sample.

Conclusion

The ras2tiff command is a useful tool for converting Sun rasterfiles to TIFF files. By understanding the syntax, options, and common use cases of the ras2tiff command, you can effectively use it to manage and convert raster images.

Whether you are a developer, system administrator, or graphic designer, the ras2tiff command provides valuable functionality for working with image files in Linux.