Introduction

There is a certain desire, e.g., ¹ ² ³ and more, to embed non-vector graphics in the source document for a LaTeX document.

I haven’t yet tried ⁴ but it should do the for most use-cases, but it requires an external command to do its magic.

My idead was to use TikZ to draw a bitmap with single aquares. It’s not the most efficient, but for spares images it could be good enough.

Working Example

There’s not a lot to go through, the solution was proposed basically proposed here⁵.

Overall LaTeX File

The minimal working examples (MWE) for a TikZ image follows. The external file mwe2h.tex defines the \pixels.

\documentclass{article}
\usepackage{tikz}
\usepackage{tikzscale}

\input{mwe2h}

\begin{document}

Now whenever we want to create a TikZ diagram we need to use the tikzpicture environment.

\begin{figure}
\centering
\resizebox{7cm}{!}{%
\begin{tikzpicture}
  \foreach \line [count=\y] in \pixels {
    \foreach \pix [count=\x] in \line {
      %\draw[fill=pixel \pix] (\x,-\y) rectangle +(1,1);
	    \filldraw[fill=c\pix, draw=c\pix] (\x,-\y) rectangle +(1,1);
    }
  }
\end{tikzpicture}
}
\end{figure}

\end{document}

Transforming the Picture

The .png image is converted to a PPM image using run-of-the-mill convert from ImageMagick. The following Python script then turns that into a LaTeX array.

"""This is a crude hack to convert ppm files to tikz"""
import hashlib
from collections import defaultdict


def parse_ppm_file(file_path):
    with open(file_path, 'rb') as ppm_file:
        header = ppm_file.readline()
        width, height = map(int, ppm_file.readline().split())
        max_val = int(ppm_file.readline())

        data = ppm_file.read()

    pixel_values = []
    colours = defaultdict(int)
    for i in range(0, len(data), 3):
        r = data[i]
        g = data[i + 1]
        b = data[i + 2]
        colours[(r,g,b)] += 1
        pixel_values.append((r, g, b))

    return pixel_values, width, height, colours


def generate_tikz_file(file_path, pixels, width, height, colourmap):
    with open(file_path + ".tex", 'w') as tikz_file:
        tikz_file.write("\\begin{tikzpicture}\n")

        maxkey = max(colourmap, key=colourmap.get)
        maxval = colourmap[maxkey]
        tikz_file.write("% max value: {} {}\n".format(maxkey, maxval))
        for colours, numbers in colourmap.items():
            if numbers:
                htmlcolour = "{:02x}{:02x}{:02x}".format(colours[0], colours[1], colours[2])
                key = htmlcolour
                tikz_file.write("\\definecolor{{c{}}}{{HTML}}{{{}}} % {}\n".format(key, htmlcolour, numbers))
        tikz_file.write("\\def\\pixels{\n")
        for y in range(height):
            xlist = []
            for x in range(width):
                # if pixels[y * width + x] == maxkey:
                #     continue
                r, g, b = pixels[y * width + x]
                htmlcolour = "{:02x}{:02x}{:02x}".format(r, g, b)
                key = htmlcolour
                # tikz_file.write("\\filldraw[fill=c{}, draw=c{}] ({},-{}) rectangle +(1,1);\n".format(key, key, x, y))
                xlist.append(htmlcolour)
            tikz_file.write("{{{}}},\n".format(",".join(xlist)))
        tikz_file.write("}\n")
        tikz_file.write("\\end{tikzpicture}\n")

if __name__ == "__main__":
    import sys

    if len(sys.argv) != 2:
        print("Usage: python parse_ppm.py <filename>")
        sys.exit(1)

    file_path = sys.argv[1]
    pixels, width, height, colourmap = parse_ppm_file(file_path)

    tikz_file_path = ".".join(file_path.split('.')[:-1])  # Remove the file extension
    generate_tikz_file(tikz_file_path, pixels, width, height, colourmap)

Alternatives

PxPic

https://ctan.org/pkg/pxpic

Lines

It will reduce the size of the result if just was used⁶. That doesn’t look particularly good though.

Post-Script

Reading through the references mentioned hereafter, it seems as if EPS files acould be embedded. Another item on the backlog.

Summary

This works, but barely and doesn’t solve the problem to a adequate degree.

Adventures in TikZ-Land