<\/p>\n
<\/p>\n
The short version: A few lines of Python<\/a> code using the Matplotlib<\/a> library will convert between HSV<\/a> and RGB<\/a> colour values. An online tool is not required.<\/p>\n For example, the open source keyboard firmware QMK<\/a> tends to use HSV values instead of RGB. Some common values are in file color.h<\/a><\/em>.<\/p>\n A trap for young players: Many online tools and code snippets don’t reveal what units they use (and thus expect) for HSV. For example, there is a difference between the formal<\/em><\/strong> HSV values and those scaled to fit the range for a byte (0-255). The latter is used in QMK. For RGB values, there isn’t any ambiguity (as far as I know).<\/p>\n One option is using Python. The Python library Matplotlib<\/a> is used here, but it may not be installed by default:<\/p>\n On Debian<\/a>-like systems (for example, LMDE<\/a>, Linux Mint<\/a>, Ubuntu<\/a>, Debian itself, Lubuntu<\/a>, Kubuntu<\/a>, Xubuntu<\/a>, BunsenLabs<\/a>, Linux Lite<\/a>, WSL<\/a>, etc.), install it by:<\/p>\n On a newer Linux system, you will probably get something like this error message:<\/p>\n This cryptic error message (it does not even identify itself as an error message) means that it is too risky to change the global<\/em><\/strong> Python installation, as the operating system has become too dependent on Python (the operating system may become completely inoperable, requiring a reinstallation).<\/p>\n Instead, the change can be isolated by using a so-called virtual Python environment (so the system\/global Python installation is not affected):<\/p>\n Module ‘venv’ is probably installed by default. If it isn’t, it can be installed by:<\/p>\n After use, exit the virtual Python environment:<\/p>\n As an alternative method to the overhead and complexity of a virtual Python environment, including starting and exiting the virtual Python environment, a newfangled method is using ‘uv<\/a>‘ (a terrible, terrible name is the search engine era). It hides all the virtual Python stuff and takes take of it automatically. Thus, it appears<\/em><\/strong> to install Matplotlib globally, but behind the scenes it doesn’t.<\/p>\n With Matplotlib installed, to convert, for example, interactively, from the command line on, for Linux:<\/p>\n On some Linux systems, this is instead executable ‘python3’ (both newer and older Linux systems). In a virtual Python environment, ‘python’ may work fine, even if it doesn’t for the global Python installation.<\/p>\n After use, exit the interactive session:<\/p>\n Convert an HSV value to RGB (before the exit):<\/p>\n Notes:<\/p>\n And for HSV_TURQUOISE (0x7B5A70)<\/a> = RGB_TURQUOISE (0x476E6A)<\/a> from the QMK project, converting from RGB to HSV:<\/p>\n Note some advantages of this Python method:<\/p>\n The discrepancy for value, V<\/a> (brightness), 112 vs. 110 seems to be too high. Perhaps the QMK values are in error?<\/p>\n <\/p>\n For example, on Keychron keyboards, probably depending on the model, for the same current, the red LEDs are only about half as bright as the blue and green LEDs.<\/p>\n So the idea is to scale the RGB values recipocally, optionally rescaling the brightness to the maximum (convert to HSV, set the ‘V’ to 255 and convert back to RGB).<\/p>\n <\/p>\n <\/p>\n","protected":false},"excerpt":{"rendered":" The short version: A few lines of Python code using the Matplotlib library will convert between HSV and RGB colour values. An online tool is not required. For example, the open source keyboard firmware QMK tends to use HSV values …<\/p>\nUsing Python<\/h2>\n
\r\nImportError: No module named matplotlib\r\n<\/pre>\n
\r\nsudo apt update\r\nsudo pip install matplotlib\r\n<\/pre>\n
\r\nThis environment is externally managed\r\n<\/pre>\n
\r\n# Create the virtual Python environment\r\npython3 -m venv ~\/.our_Matplotlib_environment\r\n\r\n# Enter the virtual Python environment\r\nsource ~\/.our_Matplotlib_environment\/bin\/activate\r\n\r\n# Install Matplotlib\r\npip install matplotlib\r\n<\/pre>\n
\r\nsudo apt update\r\nsudo apt install python3-venv python3-pip\r\n<\/pre>\n
\r\n# Exit the virtual Python environment\r\ndeactivate\r\n<\/pre>\n
The actual conversion<\/h3>\n
\r\npython\r\n<\/pre>\n
\r\nquit()\r\n<\/pre>\n
\r\nimport matplotlib\r\nimport numpy as np # For set_printoptions()\r\n\r\nnp.set_printoptions(precision=4) # With byte values,\r\n # 0-255, not more than 4 is warranted\r\n\r\n# Quarter intensity for pure HSV RED\r\n# (hue = 0 degrees, scaled to\r\n# [0.0; 1.0] for 360 degrees)\r\n256 * matplotlib.colors.hsv_to_rgb([[[0 \/ 256, 256 \/ 256, 256 \/ 256 \/ 4]]])\r\n# Result: array([[[64., 0., 0.]]]),\r\n# that is, RGB value 400000\r\n#\r\n<\/pre>\n
\n
\r\nimport matplotlib\r\nimport numpy as np # For set_printoptions()\r\n\r\nnp.set_printoptions(precision=4) # With byte values,\r\n # 0-255, not more than 4 is warranted\r\n\r\n# RGB_TURQUOISE (0x476E6A, 71, 110, 106) =\r\n# HSV_TURQUOISE (0x7B5A70, 123, 90, 112)\r\n#\r\nhsv2 = 255 * matplotlib.colors.rgb_to_hsv(\r\n [[[0x47 \/ 255, 0x6E \/ 255, 0x6A \/ 255]]])\r\nhsv2\r\n# Result: array([[[123.141 , 90.4091, 110.]]])\r\n\r\n# As hexadecimal HSV values rounded\r\n# to the nearest integer:\r\nprint(f"{round(hsv2[0, 0, 0]):02X}")\r\nprint(f"{round(hsv2[0, 0, 1]):02X}")\r\nprint(f"{round(hsv2[0, 0, 2]):02X}")\r\n\r\n# Or formatted as an HSV hexadecimal value,\r\n# followed by the three decimal numbers,\r\n# plus the angle (0-360) for hue:\r\n#\r\nprint(f"HSV 0x{round(hsv2[0, 0, 0]):02X}{round(hsv2[0, 0, 1]):02X}{round(hsv2[0, 0, 2]):02X}, {round(hsv2[0, 0, 0])} (angle {round(hsv2[0, 0, 0]\/255*360)}), {round(hsv2[0, 0, 1])}, {round(hsv2[0, 0, 2])}")\r\n#\r\n# Output:\r\n#\r\n# HSV 0x7B5A6E, 123 (angle 174), 90, 110\r\n#\r\n<\/pre>\n\n
Bonus: Handling unbalanced RGB LEDs<\/h2>\n
References<\/h2>\n
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