Get a ggplot2 color scheme based on the RGB pixel values of an image/logo

set_color_theme.R

# Sets theme according to color of logo
set_color_theme <- function(logo_loc, low_sat = 0.042, high_sat = 0.866, medium_sat = 0.28, 
                            low_val = 0.99, high_val = 0.38, medium_val = 0.65) {  
    # Read image/logo as a list
    img1 <- list(readPNG(file.path(logo_loc)))
    # Find the average pixel value
    rgb <- rowMeans(sapply(img1, function(im) apply(im, 3, mean) * 255))
    # Convert to HSV - hue, saturation, value
    img_hsv <- rgb2hsv(rgb[1:3])[,1]
    
    # Plot theme - Keeping the hue(color) values the same, saturation (purity) and value (dark/light) are increased or decreased.
    # lighter color for the plot background
    bckgrnd_color <- hsv2rgb(img_hsv[1] * 360, min(low_sat, img_hsv[2]), max(low_val, img_hsv[3]))  
    # darker color for the axis labels/text 
    label_color <- hsv2rgb(img_hsv[1] * 360, max(high_sat, img_hsv[2]), min(high_val, img_hsv[3])) 
    # middle color for lines/points on plot 
    points_color <- hsv2rgb(img_hsv[1] * 360, min(medium_sat, img_hsv[2]), ifelse(img_hsv[3] < 0.5, 0.5, min(medium_val, img_hsv[3]))) 
    
    return(list("img_rgb" =  rgb(rgb[1], rgb[2], rgb[3], maxColorValue = 255), "bckgrnd_color" = bckgrnd_color, "label_color" = label_color, "points_color" = points_color))
}