Problem Computing Dot Product with mir

Kyle Ingraham kyle at kyleingraham.com
Tue Feb 23 02:59:10 UTC 2021


On Monday, 22 February 2021 at 07:14:26 UTC, 9il wrote:
> On Sunday, 21 February 2021 at 16:18:05 UTC, Kyle Ingraham 
> wrote:
>> I am trying to convert sRGB pixel values to XYZ with mir using 
>> the following guide: 
>> http://www.brucelindbloom.com/index.html?Eqn_RGB_XYZ_Matrix.html
>>
>> [...]
>
> mir-glas is deprecated experimental project. It is worth use 
> mir-blas or lubeck instead. There is also naming issue. In the 
> classic BLAS naming dot refers a function that accept two 1D 
> vectors.

Your suggestion worked beautifully. I went with lubeck. I don't 
know how I missed it seeing that it is right there in the Dlang 
tour.

Thank you for writing such useful libraries.

Final code ended up being:

import std.stdio;

import kaleidic.lubeck: mtimes;
import mir.ndslice: as, byDim, fuse, map, sliced;

void main()
{
	auto rgbToXyz = [0.4124564,  0.3575761,  0.1804375,
					 0.2126729,  0.7151522,  0.0721750,
  					 0.0193339,  0.1191920,  0.9503041]
  		.as!double
		.sliced(3, 3);

	ubyte[] rgbPixels = [255, 0, 0,
	 			 		 0, 255, 0,
	  			 		 0, 0, 255,
	   			 		 120, 120, 120];

	auto xyzPixels = rgbPixels
		// convert input array elements to double - lazy
		.as!double
		// create a slice-shell over the input array
		.sliced(2, 2, 3)
		// normalize pixel channels to range [0, 1]
		.map!(chnl => chnl / 255.0)
		// sRGB inverse compand
		.map!(chnl => chnl <= 0.04045 ? chnl / 12.92 : ((chnl + 0.055) 
/ 1.055) ^^ 2.4)
		// linear RGB to XYZ
		// iterator by x and y over pixels (3rd dimension)
		.byDim!(0, 1) // same as .pack!1
		// dot product of each pixel with conversion matrix
		.map!(pixel => mtimes(rgbToXyz, pixel))
		// join iterator values into a matrix
		.fuse;

	xyzPixels.writeln;
	xyzPixels.shape.writeln;
}


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