Gray glsl filter with video capture

[monkstone]

On a bit of roll with glsl filters and video capture on my RaspberryPI4. Previously people have reported issues using regular processing filters with video capture:-

1. Opengl and face OSC
2. Filter with glvideo

Here is another glsl video capture sketch, this time in ruby (using my PiCrate gem):-

require 'picrate'

class Gray < Processing::App
	load_library :video

	attr_reader :gray, :cam

	def settings
	  size(640, 480, P2D)
	end 

	def setup
	sketch_title 'Grayscale'
	  @gray = load_shader(data_path('gray.glsl'))
          gray.set('sketchSize', width.to_f, height.to_f)
	  start_capture(width, height)
	end

	def start_capture(w, h)
	  @cam = Java::ProcessingVideo::Capture.new(self, w, h, "UVC Camera (046d:0825)")
	  cam.start
	end

	def draw
	  return unless cam.available

          cam.read
          image(cam, 0, 0)
          return if mouse_pressed?
          filter(gray)
	end
		
	def captureEvent(c)
	  c.read
	end
end


Gray.new

and the glsl code

#ifdef GL_ES
precision mediump float;
precision mediump int;
#endif
#define GRAY vec3(0.299, 0.597, 0.114)

uniform sampler2D texture; // iChannel0 in Shadertoy
uniform vec2 sketchSize; // iResolution in Shadertoy

void main() {
    vec2 uv = gl_FragCoord.xy / sketchSize.xy;
    gl_FragColor = vec4(vec3(dot(texture2D(texture, uv).xyz, GRAY)), 1.);
}