convert

The convert program is a member of the ImageMagick suite of tools. Use it to convert between image formats as well as resize an image, blur, crop, despeckle, dither, draw on, flip, join, re-sample, and much more.

Documentation

• Documentation [EN]
• ImageMagick Examples - Resize or Scaling [EN]

• man 1 'convert' [EN]

Parameters

-alpha TYPE

Gives control of the alpha/matte channel of an image.

-background COLOR

Set the background COLOR.

-border GEOMETRY

Surround the image with a border of color.

-bordercolor COLOR

Set the border COLOR.

-colors NUMBER

Set the preferred NUMBER of colors in the image.

-define KEY{=VALUE} [...]

Add specific global settings generally used to control coders and image processing operations.

-define 'filter:support=RADIUS'

Set the filter support RADIUS. Defines how large the filter should be and thus directly defines how slow the filtered resampling process is.

-define 'png:compression-filter=VALUE'

Valid VALUEs are 0 through 9. 0-4 are the corresponding PNG filters, 5 means adaptive filtering except for images with a colormap, 6 means adaptive filtering for all images, 7 means MNG 'loco' compression, 8 means Z_RLE strategy with adaptive filtering, and 9 means Z_RLE strategy with no filtering.

-define 'png:compression-level=VALUE'

Valid VALUEs are 0 through 9, with 0 providing the least but fastest compression and 9 usually providing the best and always the slowest.

-delete INDEX

Delete the images specified by index, from the image sequence.

-fill COLOR

COLOR to use when filling a graphic primitive.

-font NAME

Set the font to use when annotating images with text, or creating labels.

-interlace TYPE

The TYPE of interlacing scheme.

-pointsize NUMBER

Pointsize of the Postscript, OPTION1, or TrueType font.

-quality LEVEL

JPEG/PNG compression LEVEL.

-resize GEOMETRY

Resize an image to GEOMETRY.

-strip

Strip the image of any profiles or comments.

-trim

Trim an image.

Examples

Convert an image to another format

if type -P 'convert' >'/dev/null' 2>&1; then
  my::convert_images() {
    for old_file in *.$(sed 's/./[&\u&]/g' <<< "$1"); do
      local new_file="${old_file,,}"; new_file="${new_file/%$1/$2}"

      if [[ -f "${new_file}" ]]; then
        my::carp "'${new_file}' already exists"
        continue
      fi

      if convert -strip "${old_file}" "${new_file}" >'/dev/null' 2>&1; then
        echo "Convert '${old_file}' => '${new_file}'"

        rm "${old_file}"
      else
        my::carp "'${file}' can't be converted"
        return 1
      fi
    done
  }

  alias my::gif2png='my::convert_images "gif" "png"'
  alias my::png2jpg='my::convert_images "png" "jpg"'
fi

Create a favicon

convert 'image.png' -bordercolor 'white' -border 0 \
  \( -clone 0 -resize '16x16' \) \
  \( -clone 0 -resize '32x32' \) \
  \( -clone 0 -resize '48x48' \) \
  \( -clone 0 -resize '64x64' \) \
  -delete 0 -alpha 'off' -colors 256 'favicon.ico'