We need a PHP function that generates histograms and scattergrams.
In the case of histograms, the parameters "data" and "fill_color" are always present and, optionally, a parameter "thresholds" can be present. The parameter "data" is a sequence of hexadecimal values representing each point of the histogram curve on the y-axis, where each hexadecimal value consists of two ASCII characters. Let's say we have the string 5B97B9. In a coordinate system, this would give a value of 91 for the first data point (x = 1; y = 91), a value of 151 for the second point (x = 2; y = 151), and a value of 185 for the third point (x = 3; y = 185). A line chart should be drawn for these data points.
The optional parameter "thresholds" is a data stream of hexadecimal values representing reference values. These would have to be drawn on the diagram as vertical dashed lines. If we take the string 142C in hexadecimal notation as an example, we would have the decimal values 20 and 44 in this case; correspondingly, dashed lines would have to be drawn for the x-values 20 and 44.
The resulting image should always be 600 * 600 pixels. The x-axis should be labeled with units. Depending on the measurement parameters, there can be different maximum values in the x or y direction. The diagram would therefore have to be scaled accordingly depending on the measuring range. The area below the line should be colored in the hex-coded fill color passed to the function (e.g. ff0000).
Attached you can see an example how the histogram should look like.
In the case of a scattergram, the function should take four parameters: "x_coordinates", "y_coordinates", "pulse_count" and "population_type". The raw data of scattergrams has a grid size of 256 * 256 pixels. The base point is at the top (!) left. Analogous to histograms, all four parameters contain a data stream with hex-coded values, with each value representing a pixel of the scattergram. The x- and y-coordinates of the raw data are between 0 and 255. The pulse count is the number of pulses for each pixel at the same location and can have values between 1 and 31; the higher the number of pulses, the more intense the color of the respective pixel should be. Each population type should be given its own specific color code, which can be one of the following values:
This would mean that the first pixel has the x-coordinate 113 and the y-coordinate 81, a pulse count (color intensity) of 21 and belongs to population 2.
The result should look like the attached image.
The base point in the generated image should be at the bottom (!) left. Distinctly different colors should be used for each of the seven population types. Within each population there are different color intensities depending on the number of pulses.
A legend would have to be integrated for the individual population groups if the respective population group occurs in a scattergram. This can be done as in the example attached, although the calculation of the respective placement might be a bit tricky. It would also be okay if a legend with the assignment of the corresponding color code to a population type is integrated below the scattergram.
The resulting image of the actual scattergram should be 600 * 600 pixels in size. If the legend is placed below the scattergram, an additional space of about 200 pixels in height can be used for it.
Both the histograms and the scattergrams should be drawn on a white background with black axes. The images should be generated as PNGs and returned by the function as a string.
The code should be fully compatible with PHP 8.2. Either two separate functions or one function can be developed for the histogram and scattergram. The code should work with PHP's integrated functions, so no external libraries should be used for it.
