Simplify orx-jumpflood api

orx-jumpflood/src/main/resources/shaders/gl3/pixel-direction.frag

@@ -0,0 +1,16 @@
+#version 330 core
+
+uniform sampler2D tex0;
+uniform sampler2D tex1;
+in vec2 v_texCoord0;
+
+out vec4 o_color;
+
+void main() {
+    vec2 size = textureSize(tex0, 0);
+    vec2 pixelPosition = v_texCoord0;
+    vec2 centroidPixelPosition = texture(tex0, v_texCoord0).xy;
+    vec2 pixelDistance = (centroidPixelPosition - pixelPosition) * size * vec2(1.0, -1.0);
+    float threshold = texture(tex1, v_texCoord0).r;
+    o_color = vec4(pixelDistance, threshold, 1.0);
+}