This post illustrates how to create a CIR image from an input RGBI TIFF file. In order to generate a CIR image, the input channels - RGBI has to be reordered to IRG i.e.
- the file's output red channel is replaced with the input Infra red channel,
- the output green channel is replaced with the input red channel,
- the output's green channel is replaced with the input green channel,
- and the input blue channel is essentially thrown away.
The ImageMagick command to do this is quite simple, as shown below.
$ convert input_rgbi.tif -channel rgba -separate -swap 1,2 -swap 0,1 -swap 0,3 -channel rgb -combine output_cir.tif
Note: the sequence of options is important.
- The option -channel rgba instructs the command to read in 4 channels.
- The option -separate splits the input channels
- The option -swap 1,2 swaps the 2nd and 3rd channels from RGBI to RBGI
- The option -swap 0,1 swaps the 1st and 2nd channels from RBGI to BRGI
- The option -swap 0,3 swaps the 1st and 4th channels from BRGI to IRGB
- The option -rgb removes the 4th channel to become IRG
- The option -combine merges all the 3 channels back
|The input RGBI file (only the RGB channels are displayed)|
|The CIR image generated from ImageMagick|