Imagemagick Tips

ImagemagickTips.txt

# Separate an image into RGB channels. Filenames 1, 2, 3 for red, green and blue respectively
convert image.jpg  -channel RGB  -separate  channels_%d.png

# Convert an image to grayscale
convert image.jpg -set colorspace Gray -separate -average image.png

# Threshold an image
convert -threshold 75 image.jpg image-thresh.jpg

# Combine images using max pixel values of each image
convert  image1.jpg  image2.jpg  -evaluate-sequence max  image.png

# Average a set of fits files
convert image*.fits -evaluate-sequence mean -define quantum:format=floating-point -depth 32 result.fits


# Subtract a dark image from an image - 2 methods
convert dark.png image.png -evaluate-sequence subtract result.png
convert dark.png image.png -compose minus -composite result.png

# Watermark an image in lower right corner
convert -fill grey -transparent white -font "Liberation-Sans" -pointsize 96 label:"Watermark" -shade 120x45 watermark.png
composite -watermark 50% -gravity SouthEast -geometry +20+20 watermark.png image.jpg image-watermarked.png

########################################
# Large copyright watermark stamp an image
# Create a large copyright symbol
convert -size 1200x800 -gravity West -fill black -transparent white -font Arial -pointsize 800 label:"©" -shade 240x40 copyright.png
# Create the copyright name to fit inside
convert -fill black -transparent white -font Arial -pointsize 96 label:"Owner's Name" -shade 240x40 name.png
# Compose the 2 images in one watermark stamp
composite -gravity Center -geometry -25-20 name.png copyright.png stamp.png
# Add the watermark stamp to the main image
composite -watermark 15% -gravity South -geometry +20+200 stamp.png image.jpg stamped.jpg
########################################

# Overlay one image on another
convert input.png trees.png -gravity south -composite result.png

# Apply a scale function to an image. This power function improves bright lunar images
convert -fx "pow(u,4)" image.jpg image_pow.jpg

# Copy EXIF tags from one image to another
exiftool -TagsFromFile image1.jpg image2.jpg

# Change the EXIF time on an image
image_time="2019:10:02 20:06:34.33-05:00" exiftool -m -xmp:dateTimeOriginal=$image_time -xmp:dateTimeDigitized=$image_time -exif:dateTimeOriginal=$image_time -exif:dateTimeDigitized=$image_time image.jpg

# Overlay the filename on the image
convert input.jpg -gravity Southwest -pointsize 12 -fill white -annotate 0 '%f' output.jpg

# Rotate an image by 1 degree
convert input.jpg -distort ScaleRotateTranslate 1 +repage output.jpg

# Crop a white border around an image
convert input.png -flatten -fuzz 25% -trim +repage cropped.png