pdf

Use these notes to evaluate the resulting PDF from atlante.

Verify Raster & Vector Data in the PDF stream

Discussion on how to analyze PDFs from Maptoolkit after they have been generated. The command line tool is called mutool from mupdf.com. The data extracted can be used to:

• Verify the resolution (pixels per inch) is sufficient for printing
• Verify atlante command lines such as --dpi
• Verify the True Type Fonts used
• Inspect image width and height

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Extract

Extract images and font files from a PDF using mutool extract. Output is *.ttf, *.png.

• brew install mupdf-tools # macOS
• Or, https://mupdf.com
  • https://www.mankier.com/1/mutool
  • https://www.mupdf.com/docs/

Example Usage

# extract
mutool extract output.pdf

# brew install tree     # macOS
#  Output  from `tree .`

├── BXHVIO+<root-font-name>-0019.ttf    #  TTF file 1/2
├── YKBIWE+<root-font-name>-0014.ttf    #  TTF file 2/2
├── output.pdf                          # this is the original PDF
├── img-0007.png                        # this is the png data that was in the PDF stream

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Image Size

Using Image Magick, list the image dimensions.

# brew install imagemagick  # macOS
# Basic usage
#   magick identify                 img-0007.png
#   magick identify -verbose  -ping img-0007.png

PNG_FILE=img-0007.png
# with formatting
#   Result:  width x height = 8563 x 5076
magick identify -format "width x height = %w x %h\n" $PNG_FILE

# Image Magick can convert from pixels to inches
# ppi=72
#   Result:  118.931 by 70.5 inches
magick identify -format "%[fx:w/72] by %[fx:h/72] inches\n" $PNG_FILE

# ppi=144
#   Result:  59.4653 by 35.25 inches
magick identify -format "%[fx:w/144] by %[fx:h/144] inches\n" $PNG_FILE

# ppi=288
#   Result:  29.7326 by 17.625 inches
magick identify -format "%[fx:w/288] by %[fx:h/288] inches\n" $PNG_FILE

# ppi=300
#   28.5433 by 16.92 inches
magick identify -format "%[fx:w/300] by %[fx:h/300] inches\n" $PNG_FILE

Comparison of the SVG Template to the resulting PNG

The SVG template is used to compute the image dimensions. You can use this command to see what was computed in the output.svg.

cat output.svg | grep image

# result, units are SVG units, or points
  # <image width="140.75" height="269"  xlink:href="output.png"/>

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Example NOAA PDF Charts

Analysis of NOAA PDF charts

• As of Summer 2019, a NOAA Notice to Mariners is a 400 ppi image with no fonts nor vector data
• From https://www.charts.noaa.gov/InteractiveCatalog/nrnc.shtml
• wget https://charts.noaa.gov/PDFs/18773.pdf # San Diego

Using mutool to analyze NOAA Chart - 18773

# Page Size from macOS Preview
#   48.77 × 35.27 inches

# Extract data from NOAA chart around San Diego
mutool extract 18773.pdf


# `tree .`
#   └── img-0002.png
#   0 directories, 1 file

# Compute width x height for the resulting PNG
PNG_FILE=img-0002.png
magick identify -format "width x height = %w x %h\n" $PNG_FILE
# result
#   width x height = 19504 x 14108

# Pixels Per Inch calcuations
# 19504 / 48.77 = 400 ppi
# 14108 / 35.27 = 400 ppi