Add filter shader hooks

src/image/filterRenderer2D.js

@@ -14,6 +14,11 @@ import filterThresholdFrag from '../webgl/shaders/filters/threshold.frag';
 import filterShaderVert from '../webgl/shaders/filters/default.vert';
 import { filterParamDefaults } from "./const";
 
+
+import filterBaseFrag from "../webgl/shaders/filters/base.frag";
+import filterBaseVert from "../webgl/shaders/filters/base.vert";
+import webgl2CompatibilityShader from "../webgl/shaders/webgl2Compatibility.glsl";
+
 class FilterRenderer2D {
   /**
    * Creates a new FilterRenderer2D instance.
@@ -27,7 +32,12 @@ class FilterRenderer2D {
     this.canvas.height = pInst.height;
 
     // Initialize the WebGL context
-    this.gl = this.canvas.getContext('webgl');
+    let webglVersion = constants.WEBGL2;
+    this.gl = this.canvas.getContext('webgl2');
+    if (!this.gl) {
+      webglVersion = constants.WEBGL;
+      this.gl = this.canvas.getContext('webgl');
+    }
     if (!this.gl) {
       console.error("WebGL not supported, cannot apply filter.");
       return;
@@ -38,7 +48,7 @@ class FilterRenderer2D {
       registerEnabled: new Set(),
       _curShader: null,
       _emptyTexture: null,
-      webglVersion: 'WEBGL',
+      webglVersion,
       states: {
         textureWrapX: this.gl.CLAMP_TO_EDGE,
         textureWrapY: this.gl.CLAMP_TO_EDGE,
@@ -54,6 +64,8 @@ class FilterRenderer2D {
       },
     };
 
+    this._baseFilterShader = undefined;
+
     // Store the fragment shader sources
     this.filterShaderSources = {
       [constants.BLUR]: filterBlurFrag,
@@ -90,6 +102,45 @@ class FilterRenderer2D {
     this._bindBufferData(this.texcoordBuffer, this.gl.ARRAY_BUFFER, this.texcoords);
   }
 
+  _webGL2CompatibilityPrefix(shaderType, floatPrecision) {
+    let code = "";
+    if (this._renderer.webglVersion === constants.WEBGL2) {
+      code += "#version 300 es\n#define WEBGL2\n";
+    }
+    if (shaderType === "vert") {
+      code += "#define VERTEX_SHADER\n";
+    } else if (shaderType === "frag") {
+      code += "#define FRAGMENT_SHADER\n";
+    }
+    if (floatPrecision) {
+      code += `precision ${floatPrecision} float;\n`;
+    }
+    return code;
+  }
+
+  baseFilterShader() {
+    if (!this._baseFilterShader) {
+      this._baseFilterShader = new Shader(
+        this._renderer,
+        this._webGL2CompatibilityPrefix("vert", "highp") +
+          webgl2CompatibilityShader +
+          filterBaseVert,
+        this._webGL2CompatibilityPrefix("frag", "highp") +
+          webgl2CompatibilityShader +
+          filterBaseFrag,
+        {
+            vertex: {},
+            fragment: {
+              "vec4 getColor": `(FilterInputs inputs, in sampler2D canvasContent) {
+                return getTexture(canvasContent, inputs.texCoord);
+              }`,
+            },
+          }
+      );
+    }
+    return this._baseFilterShader;
+  }
+
   /**
    * Set the current filter operation and parameter. If a customShader is provided,
    * that overrides the operation-based shader.

src/webgl/material.js

@@ -1520,6 +1520,82 @@ function material(p5, fn){
     return this._renderer.baseMaterialShader();
   };
 
+  /**
+   * Get the base shader for filters.
+   *
+   * You can then call <a href="#/p5.Shader/modify">`baseFilterShader().modify()`</a>
+   * and change the following hook:
+   *
+   * <table>
+   * <tr><th>Hook</th><th>Description</th></tr>
+   * <tr><td>
+   *
+   * `vec4 getColor`
+   *
+   * </td><td>
+   *
+   * Output the final color for the current pixel. It takes in two parameters:
+   * `FilterInputs inputs`, and `in sampler2D canvasContent`, and must return a color
+   * as a `vec4`.
+   *
+   * `FilterInputs inputs` is a scruct with the following properties:
+   * - `vec2 texCoord`, the position on the canvas, with coordinates between 0 and 1. Calling
+   *   `getTexture(canvasContent, texCoord)` returns the original color of the current pixel.
+   * - `vec2 canvasSize`, the width and height of the sketch.
+   * - `vec2 texelSize`, the size of one real pixel relative to the size of the whole canvas.
+   *   This is equivalent to `1 / (canvasSize * pixelDensity)`.
+   *
+   * `in sampler2D canvasContent` is a texture with the contents of the sketch, pre-filter. Call
+   * `getTexture(canvasContent, someCoordinate)` to retrieve the color of the sketch at that coordinate,
+   * with coordinate values between 0 and 1.
+   *
+   * </td></tr>
+   * </table>
+   *
+   * Most of the time, you will need to write your hooks in GLSL ES version 300. If you
+   * are using WebGL 1, write your hooks in GLSL ES 100 instead.
+   *
+   * @method baseFilterShader
+   * @beta
+   * @returns {p5.Shader} The filter shader
+   *
+   * @example
+   * <div modernizr='webgl'>
+   * <code>
+   * let img;
+   * let myShader;
+   *
+   * async function setup() {
+   *   img = await loadImage('assets/bricks.jpg');
+   *   createCanvas(100, 100, WEBGL);
+   *   myShader = baseFilterShader().modify({
+   *     uniforms: {
+   *       'float time': () => millis()
+   *     },
+   *     'vec4 getColor': `(
+   *       FilterInputs inputs,
+   *       in sampler2D canvasContent
+   *     ) {
+   *       inputs.texCoord.y +=
+   *         0.01 * sin(time * 0.001 + inputs.position.x * 5.0);
+   *       return getTexture(canvasContent, inputs.texCoord);
+   *     }`
+   *   });
+   * }
+   *
+   * function draw() {
+   *   image(img, -50, -50);
+   *   filter(myShader);
+   *   describe('an image of bricks, distorting over time');
+   * }
+   * </code>
+   * </div>
+   */
+  fn.baseFilterShader = function() {
+    return (this._renderer.filterRenderer || this._renderer)
+      .baseFilterShader();
+  };
+
   /**
    * Get the shader used by <a href="#/p5/normalMaterial">`normalMaterial()`</a>.
    *

src/webgl/p5.RendererGL.js

@@ -16,6 +16,7 @@ import { ShapeBuilder } from "./ShapeBuilder";
 import { GeometryBufferCache } from "./GeometryBufferCache";
 import { filterParamDefaults } from "../image/const";
 
+import filterBaseVert from "./shaders/filters/base.vert";
 import lightingShader from "./shaders/lighting.glsl";
 import webgl2CompatibilityShader from "./shaders/webgl2Compatibility.glsl";
 import normalVert from "./shaders/normal.vert";
@@ -36,6 +37,7 @@ import imageLightVert from "./shaders/imageLight.vert";
 import imageLightDiffusedFrag from "./shaders/imageLightDiffused.frag";
 import imageLightSpecularFrag from "./shaders/imageLightSpecular.frag";
 
+import filterBaseFrag from "./shaders/filters/base.frag";
 import filterGrayFrag from "./shaders/filters/gray.frag";
 import filterErodeFrag from "./shaders/filters/erode.frag";
 import filterDilateFrag from "./shaders/filters/dilate.frag";
@@ -87,6 +89,8 @@ const defaultShaders = {
   imageLightVert,
   imageLightDiffusedFrag,
   imageLightSpecularFrag,
+  filterBaseVert,
+  filterBaseFrag,
 };
 let sphereMapping = defaultShaders.sphereMappingFrag;
 for (const key in defaultShaders) {
@@ -302,6 +306,7 @@ class RendererGL extends Renderer {
     this.specularShader = undefined;
     this.sphereMapping = undefined;
     this.diffusedShader = undefined;
+    this._baseFilterShader = undefined;
     this._defaultLightShader = undefined;
     this._defaultImmediateModeShader = undefined;
     this._defaultNormalShader = undefined;
@@ -2087,6 +2092,27 @@ class RendererGL extends Renderer {
     return this._defaultFontShader;
   }
 
+  baseFilterShader() {
+    if (!this._baseFilterShader) {
+      this._baseFilterShader = new Shader(
+        this,
+        this._webGL2CompatibilityPrefix("vert", "highp") +
+          defaultShaders.filterBaseVert,
+        this._webGL2CompatibilityPrefix("frag", "highp") +
+          defaultShaders.filterBaseFrag,
+        {
+            vertex: {},
+            fragment: {
+              "vec4 getColor": `(FilterInputs inputs, in sampler2D canvasContent) {
+                return getTexture(canvasContent, inputs.texCoord);
+              }`,
+            },
+          }
+      );
+    }
+    return this._baseFilterShader;
+  }
+
   _webGL2CompatibilityPrefix(shaderType, floatPrecision) {
     let code = "";
     if (this.webglVersion === constants.WEBGL2) {

src/webgl/p5.Shader.js

@@ -52,6 +52,79 @@ class Shader {
     };
   }
 
+  hookTypes(hookName) {
+    let fullSrc = this._vertSrc;
+    let body = this.hooks.vertex[hookName];
+    if (!body) {
+      body = this.hooks.fragment[hookName];
+      fullSrc = this._fragSrc;
+    }
+    if (!body) {
+      throw new Error(`Can't find hook ${hookName}!`);
+    }
+    const nameParts = hookName.split(/\s+/g);
+    const functionName = nameParts.pop();
+    const returnType = nameParts.pop();
+    const returnQualifiers = [...nameParts];
+
+    const parameterMatch = /\(([^\)]*)\)/.exec(body);
+    if (!parameterMatch) {
+      throw new Error(`Couldn't find function parameters in hook body:\n${body}`);
+    }
+
+    const structProperties = structName => {
+      const structDefMatch = new RegExp(`struct\\s+${structName}\\s*\{([^\}]*)\}`).exec(fullSrc);
+      if (!structDefMatch) return undefined;
+
+      const properties = [];
+      for (const defSrc of structDefMatch[1].split(';')) {
+        // E.g. `int var1, var2;` or `MyStruct prop;`
+        const parts = defSrc.trim().split(/\s+|,/g);
+        const typeName = parts.shift();
+        const names = [...parts];
+        const typeProperties = structProperties(typeName);
+        for (const name of names) {
+          properties.push({
+            name,
+            type: {
+              typeName,
+              qualifiers: [],
+              properties: typeProperties,
+            },
+          });
+        }
+      }
+      return properties;
+    };
+
+    const parameters = parameterMatch[1].split(',').map(paramString => {
+      // e.g. `int prop` or `in sampler2D prop` or `const float prop`
+      const parts = paramString.trim().split(/\s+/g);
+      const name = parts.pop();
+      const typeName = parts.pop();
+      const qualifiers = [...parts];
+      const properties = structProperties(typeName);
+      return {
+        name,
+        type: {
+          typeName,
+          qualifiers,
+          properties,
+        }
+      }
+    });
+
+    return {
+      name: functionName,
+      returnType: {
+        typeName: returnType,
+        qualifiers: returnQualifiers,
+        properties: structProperties(returnType)
+      },
+      parameters
+    };
+  }
+
   shaderSrc(src, shaderType) {
     const main = 'void main';
     let [preMain, postMain] = src.split(main);

src/webgl/shaders/filters/base.frag

@@ -0,0 +1,22 @@
+precision highp float;
+
+uniform sampler2D tex0;
+uniform vec2 canvasSize;
+uniform vec2 texelSize;
+
+IN vec2 vTexCoord;
+
+struct FilterInputs {
+  vec2 texCoord;
+  vec2 canvasSize;
+  vec2 texelSize;
+};
+
+void main(void) {
+  FilterInputs inputs;
+  inputs.texCoord = vTexCoord;
+  inputs.canvasSize = canvasSize;
+  inputs.texelSize = texelSize;
+  OUT_COLOR = HOOK_getColor(inputs, tex0);
+  OUT_COLOR.rgb *= outColor.a;
+}

src/webgl/shaders/filters/base.vert

@@ -0,0 +1,19 @@
+precision highp int;
+
+uniform mat4 uModelViewMatrix;
+uniform mat4 uProjectionMatrix;
+
+IN vec3 aPosition;
+IN vec2 aTexCoord;
+OUT vec2 vTexCoord;
+
+void main() {
+  // transferring texcoords for the frag shader
+  vTexCoord = aTexCoord;
+
+  // copy position with a fourth coordinate for projection (1.0 is normal)
+  vec4 positionVec4 = vec4(aPosition, 1.0);
+
+  // project to 3D space
+  gl_Position = uProjectionMatrix * uModelViewMatrix * positionVec4;
+}

src/webgl/shaders/webgl2Compatibility.glsl

@@ -24,3 +24,11 @@ out vec4 outColor;
 #endif
 
 #endif
+
+#ifdef FRAGMENT_SHADER
+vec4 getTexture(in sampler2D content, vec2 coord) {
+  vec4 color = TEXTURE(content, coord);
+  color.rgb /= color.a;
+  return color;
+}
+#endif