Add functions for color detection in textures

[Matyas-Pilz]

Problem

Warning: long text

My idea is: create mod with nodebox-shaped "signs"/posters (with picture), where will be universal register function and each sign could have texture with different resolution and different ratio of width and height. It will use square texture, where will be main picture and any one other color around the main picture. And the nodebox for each poster etc. will have width and height of defined side specific for main object in picture ("island" in one specific color) and some fixed thickness.

For example, mod creator defines for it in function "sea color" #aa0034ff. Thickness will be fixed as 1/20.
Nodebox will be (-left_offset/width_resolution, 0.5-thickness, -down_offset/height_resolution, right_offset/width_resolution, upper_offset/height_resolution, 0.5).
Poster 1 will have 128 x 128 px, "sea color" will be #aa0034ff. "Island" part of picture with different colors will be 11 px from left, 12 px from right, 5 px from down and 50 px from upper edge.
Poster 2 ...
Poster 3 ...

Solutions

1. Add functions for detect colors in texture from edges:
   detect_texture_color(#rrggbbaa, "texture_name.png", "up / down / left / right")

OR

Alternatives

2. create specific nodebox type ("texture_defined") with specification of texture name and "sea" color and last dimension

OR
3) create specific drawtype ("posterlike") with specification of "sea" color and last dimension

OR
4) as actually, write it everytime directly without detection of colors in texture

Additional context

No response

[Matyas-Pilz]

I would prefer solution 1 because solutions 2 and 3 are so much specific.

[SmallJoker]

So you'd like to make a bumpmap of some sort? Or is the goal to have properly colorized sides of the nodebox, like with drawtype = "signlike" or wield items?
If not - would you please provide a visual example as I cannot fully understand what your goal is. You lost me after the part with ("island" in one specific color).

[appgurueu]

Add functions for detect colors in texture from edges:
detect_texture_color(#rrggbbaa, "texture_name.png", "up / down / left / right")

It is not quite clear to me what this function would do, and why it would be useful for what you want to do, which I unfortunately still have not understood exactly.

It seems to me like you want to sort of "detect" how the "motive" of a picture is centered? Judging by this line:

"Island" part of picture with different colors will be 11 px from left, 12 px from right, 5 px from down and 50 px from upper edge.

And that is what detect_texture_color would give you? The width/height of a rectangle of maximum size starting from the given edge?

If I'm not too far off, I think detect_texture_color would be too specific a function to be generally useful. What if you want to allow some tolerance in color checking? Some different definition of how the image is to be centered? You need to be able to write your own logic.

I think what we need for this kind of use case is an image API that is exposed on client and server alike (not to be confused with textures). It should be possible to:

• Load an image from a PNG / JPG / TGA file;
• Read and write pixels efficiently - the image should be treated as a 2d array of ARGB8 colors;
• Write an image as a PNG / JPG / TGA file

Additionally, for convenience, it should be possible to get media paths and/or contents on the server (details esp. w.r.t. dynamic media t.b.d.).

Given such APIs, you would be able to implement a detect_texture_color yourself, no?

[Matyas-Pilz]

Thank you for your comments!

For example, picture bellow (it is only example picture - it could be car on yellow carpet but it isn't important). For this picture, I use
#85241aff (dark red around) as "sea color". Up of this "car" is 1 px line of #85241bff. For this picture, distance from edges are: right = 1, left = 4, down = 11, up = 6.

My plan is "use it for nodeboxes" but this could have much more other use (for example, with similar function for detection of only some color channel it could be usable for heightmap and other map properties for mapgen - for example, tree generation etc.). Ideas of specific type of nodebox or specific drawtype are smile, these are only very specific different ways to do the same (and I think that not only very specific but too much more difficult).

Tolerance of color, this is good idea... it could be specified, but my idea is for using it with zero tolerance. Thank you, this make idea for these functions:

• detect_texture_color_edge( #rrggbbaa, "texture_name.png", "up / down / left / right", tolerance mixed or {red, green, blue, mixed RGB, transparent})
• get_texture_color_channel( "red | green | blue | alfa", "texture_name.png")
• get_texture_part_color_channel( "red | green | blue | alfa", "texture_name.png", {left_down_corner_u, left_down_corner_v}, {right_up_corner_u, right_up_corner_v})
• detect_texture_color_channel_edge( "red | green | blue | alfa", number, "texture_name.png", "up / down / left / right", tolerance mixed or {red, green, blue, mixed RGB, transparent})

[Matyas-Pilz]

It means as:
"detect_color" = "detect from edge, where is any different color than..."
It does:

• detect_texture_color_edge( #rrggbbaa, "texture_name.png", "up / down / left / right", tolerance mixed or {red, green, blue, mixed RGB, transparent})
• detect_different_texture_color_edge( #rrggbbaa, "texture_name.png", "up / down / left / right", tolerance mixed or {red, green, blue, mixed RGB, transparent})