Introduction
This article describes a way for saving images into the multi-page TIFF format by applying CCITT4 compression. It also explains how to append images to existing single page or multi-page TIFF files. Before that, we will understand what is tiff and why we should use the TIFF format.
What is TIFF ?
Tagged Image FIle Format (TIFF) is a highly used file format for storing images in many image processing applications. Using TIFF, we can store several images either as a single page or as a multi-page TIFF file. We can also append new images to existing single page or multi-page TIFF files. Many compressions like CCITT3, CCITT4, are also applied to TIFF files. Image related data like scanner name, compression type, bits per pixel, and host computer name are also stored in TIFF files using tags. Due to all these benefits, TIFF files are highly used in many applications.
You can download the sample code. The sample code attached with this article shows the following two things:
- How to store multiple images into single multi-page TIFF file with CCITT4 compression.
- How to append multiple images to existing single page or multi-page TIFF files with CCITT4 compression.
The reason for storing images with the CCITT4 compression is because programmers, initially, while playing with TIFF, generally face many problems when trying to store images with the CCITT4 compression using .NET. The most common error message is "Invalid Parameter". The most probable reason for this error is that the image on which you are trying to apply CCITT4 compression is not a bi-tonal image. The CCITT4 compression is applicable to bi-tonal images only. So I have given code for converting an image to a bi-tonal image. The code given in the sample application uses .NET GDI+ classes for storing images.
How to store images into a single multi-page TIFF file with CCITT4 compression
Consider the following screen:
You can load as many images as you want by clicking the Load Images button. All these images will be shown in panels. Now, you can click the SaveAsMultipage button. A save file dialog will open, and you can specify file name and click on the Save button. If all images are successfully saved, then a message box will appear with the message "all images saved successfully". :)
How to append multiple images to existing single page or multi-page TIFF files
You can load as many images as you want by clicking the Load Images button. All these images will be shown in panels. Now you can click the AddtoExistingFile button. An open file dialog will open and you can specify a file name by selecting any TIFF file from the file system and clicking on the Save button. If all images are successfully saved, then a message box will appear with the message "all images saved successfully".
Explanation of Code
All the above operations are done by following three functions
public bool saveMultipage(Image[] bmp, string location, string type)
This function is responsible for receiving an array of images and for saving these images on the target location in multi-page TIFF file format.
public bool saveToExistingFile(string fileName, Image[] bmp, string type)
This function is responsible for appending an array of images on an existing TIFF file which is specified by the file name parameter.
public Bitmap ConvertToBitonal(Bitmap original)
This function takes a Bitmap object which is a non-bitonal image and converts that image into a bitonal image. This is required to apply CCITT4 compression. We can not apply CCITT4 compression on non-bitonal Images.
