Question

如何使用opengl shadercode增强图像的强度？目的是使生成的图像看起来比实际图像更亮。在此处找到相关的link。但这是针对Android的。

   private void CreateShaders()
    {
        /***********Vert Shader********************/
        vertShader = GL.CreateShader(ShaderType.VertexShader);
        GL.ShaderSource(vertShader, @"attribute vec3 a_position;
        varying vec2 vTexCoord;                                            
        void main() {
        vTexCoord = (a_position.xy + 1) / 2;
        gl_Position = vec4(a_position,1);

       }");
        GL.CompileShader(vertShader);

        /***********Frag Shader ****************/
        fragShader = GL.CreateShader(ShaderType.FragmentShader);
        GL.ShaderSource(fragShader, @"precision highp float;
        uniform sampler2D sTexture;
        varying vec2 vTexCoord;
        vec3 RGBtoHSV(in vec3 RGB)
        {
            vec4 P = (RGB.g < RGB.b) ? vec4(RGB.bg, -1.0, 2.0 / 3.0) : vec4(RGB.gb, 0.0, -1.0 / 3.0);
            vec4 Q = (RGB.r < P.x) ? vec4(P.xyw, RGB.r) : vec4(RGB.r, P.yzx);
            float C = Q.x - min(Q.w, Q.y);
            float H = abs((Q.w - Q.y) / (6.0 * C + Epsilon) + Q.z);
            vec3 HCV = vec3(H, C, Q.x);
            float S = HCV.y / (HCV.z + Epsilon);
            return vec3(HCV.x, S, HCV.z);
        }
        vec3 HSVtoRGB(in vec3 HSV)
        {
            float H = HSV.x;
            float R = abs(H * 6.0 - 3.0) - 1.0;
            float G = 2.0 - abs(H * 6.0 - 2.0);
            float B = 2.0 - abs(H * 6.0 - 4.0);
            vec3 RGB = clamp(vec3(R, G, B), 0.0, 1.0);
            return ((RGB - 1.0) * HSV.y + 1.0) * HSV.z;
        }

        void main ()
        {
    vec4  color = texture2D (sTexture, vTexCoord);
    float u_saturate=0.9;
    vec3 col_hsv = RGBtoHSV(color.rgb);
    col_hsv.y *= (u_saturate * 2.0);
    vec3 col_rgb = HSVtoRGB(col_hsv.rgb);   
    gl_FragColor = vec4(col_rgb.rgb, color.a);                
        }");
        GL.CompileShader(fragShader);
    }

Answer 1

如果只想增加一种颜色的强度，请在像素着色器代码中

(0,1)

绿色将变亮1.2倍。如果要更改诸如 all 的颜色强度之类的内容，则需要查看诸如HSL颜色空间之类的内容。我回答了一个问题：GLSL shader to boost the color

Answer 2

一种可能性是将RGB颜色转换为HSV (hue, saturation, value)。更改饱和度并将其转换回RGB值。

可以在RGB to HSV/HSL/HCY/HCL in HLSL上找到用于在RGB和HSV之间转换的HLSL实现。

从HLSL移植到GLSL的代码是：

从RGB到HSV：

const float Epsilon = 1e-10;

vec3 RGBtoHSV(in vec3 RGB)
{
    vec4  P   = (RGB.g < RGB.b) ? vec4(RGB.bg, -1.0, 2.0/3.0) : vec4(RGB.gb, 0.0, -1.0/3.0);
    vec4  Q   = (RGB.r < P.x) ? vec4(P.xyw, RGB.r) : vec4(RGB.r, P.yzx);
    float C   = Q.x - min(Q.w, Q.y);
    float H   = abs((Q.w - Q.y) / (6.0 * C + Epsilon) + Q.z);
    vec3  HCV = vec3(H, C, Q.x);
    float S   = HCV.y / (HCV.z + Epsilon);
    return vec3(HCV.x, S, HCV.z);
}

HSV到RGB：

vec3 HSVtoRGB(in vec3 HSV)
{
    float H   = HSV.x;
    float R   = abs(H * 6.0 - 3.0) - 1.0;
    float G   = 2.0 - abs(H * 6.0 - 2.0);
    float B   = 2.0 - abs(H * 6.0 - 4.0);
    vec3  RGB = clamp( vec3(R,G,B), 0.0, 1.0 );
    return ((RGB - 1.0) * HSV.y + 1.0) * HSV.z;
}

可以轻松地将代码集成到片段着色器中。 u_saturate是[0.0，1.0]范围内的值。 0.5表示图像保持原样。 u_saturate大于0.5，则图像饱和；如果小于0.5，则图像被漂白：

void main ()
{
    vec4 color  = texture2D (sTexture, vTexCoord);

    vec3 col_hsv = RGBtoHSV(texColor.rgb);
    col_hsv.y *= (u_saturate * 2.0);
    vec3 col_rgb = HSVtoRGB(col_hsv.rgb);

    gl_FragColor = vec4(col_rgb.rgb, color.a);
}

请参阅WebGL示例，该示例演示了效果：

(function loadscene() {

var gl, canvas, prog, bufObj = {}, textureObj, maskTextureObj;

function render(deltaMS) {

    var saturate = document.getElementById( "saturate" ).value / 100.0;

    gl.viewport( 0, 0, vp_size[0], vp_size[1] );
    gl.enable( gl.DEPTH_TEST );
    gl.clearColor( 0.0, 0.0, 0.0, 1.0 );
    gl.clear( gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT );
    var texUnit = 0;
    gl.activeTexture( gl.TEXTURE0 + texUnit );
    gl.bindTexture( gl.TEXTURE_2D, textureObj );
    ShProg.Use( progDraw );
    ShProg.SetI1( progDraw, "u_texture", texUnit );
    ShProg.SetF2( progDraw, "u_vp_size", vp_size );
    ShProg.SetF1( progDraw, "u_saturate", saturate );
    VertexBuffer.Draw( bufRect );

    requestAnimationFrame(render);
}  

function initScene() {

    canvas = document.getElementById( "texture-canvas");
    gl = canvas.getContext( "experimental-webgl" );
    //gl = canvas.getContext( "webgl2" );
    if ( !gl )
      return;

    var texCX = 128;
    var texCY = 128;
    var texPlan = [];
    for (ix = 0; ix < texCX; ++ix) {
        for (iy = 0; iy < texCY; ++iy) {
            var val_x = Math.sin( Math.PI * 6.0 * ix / texCX )
            var val_y = Math.sin( Math.PI * 6.0 * iy / texCY )
            texPlan.push( 128 + 127 * val_x, 63, 128 + 127 * val_y, 255 );
        }
    }
    
    textureObj = Texture.LoadTexture2D( "https://raw.githubusercontent.com/Rabbid76/graphics-snippets/master/resource/texture/supermario.jpg" );
      
    progDraw = ShProg.Create( 
      [ { source : "draw-shader-vs", stage : gl.VERTEX_SHADER },
        { source : "draw-shader-fs", stage : gl.FRAGMENT_SHADER }
      ] );
    progDraw.inPos = gl.getAttribLocation( progDraw.progObj, "inPos" );
    if ( progDraw.progObj == 0 )
        return;

    bufRect = VertexBuffer.Create(
    [ { data :  [ -1, -1, 1, -1, 1, 1, -1, 1 ], attrSize : 2, attrLoc : progDraw.inPos } ],
      [ 0, 1, 2, 0, 2, 3 ] );

    window.onresize = resize;
    resize();
    requestAnimationFrame(render);
}

function resize() {
    //vp_size = [gl.drawingBufferWidth, gl.drawingBufferHeight];
    vp_size = [window.innerWidth, window.innerHeight]
    //vp_size = [256, 256]
    canvas.width = vp_size[0];
    canvas.height = vp_size[1];
}

var ShProg = {
Create: function (shaderList) {
    var shaderObjs = [];
    for (var i_sh = 0; i_sh < shaderList.length; ++i_sh) {
        var shderObj = this.Compile(shaderList[i_sh].source, shaderList[i_sh].stage);
        if (shderObj) shaderObjs.push(shderObj);
    }
    var prog = {}
    prog.progObj = this.Link(shaderObjs)
    if (prog.progObj) {
        prog.attrInx = {};
        var noOfAttributes = gl.getProgramParameter(prog.progObj, gl.ACTIVE_ATTRIBUTES);
        for (var i_n = 0; i_n < noOfAttributes; ++i_n) {
            var name = gl.getActiveAttrib(prog.progObj, i_n).name;
            prog.attrInx[name] = gl.getAttribLocation(prog.progObj, name);
        }
        prog.uniLoc = {};
        var noOfUniforms = gl.getProgramParameter(prog.progObj, gl.ACTIVE_UNIFORMS);
        for (var i_n = 0; i_n < noOfUniforms; ++i_n) {
            var name = gl.getActiveUniform(prog.progObj, i_n).name;
            prog.uniLoc[name] = gl.getUniformLocation(prog.progObj, name);
        }
    }
    return prog;
},
AttrI: function (prog, name) { return prog.attrInx[name]; },
UniformL: function (prog, name) { return prog.uniLoc[name]; },
Use: function (prog) { gl.useProgram(prog.progObj); },
SetI1: function (prog, name, val) { if (prog.uniLoc[name]) gl.uniform1i(prog.uniLoc[name], val); },
SetF1: function (prog, name, val) { if (prog.uniLoc[name]) gl.uniform1f(prog.uniLoc[name], val); },
SetF2: function (prog, name, arr) { if (prog.uniLoc[name]) gl.uniform2fv(prog.uniLoc[name], arr); },
SetF3: function (prog, name, arr) { if (prog.uniLoc[name]) gl.uniform3fv(prog.uniLoc[name], arr); },
SetF4: function (prog, name, arr) { if (prog.uniLoc[name]) gl.uniform4fv(prog.uniLoc[name], arr); },
SetM33: function (prog, name, mat) { if (prog.uniLoc[name]) gl.uniformMatrix3fv(prog.uniLoc[name], false, mat); },
SetM44: function (prog, name, mat) { if (prog.uniLoc[name]) gl.uniformMatrix4fv(prog.uniLoc[name], false, mat); },
Compile: function (source, shaderStage) {
    var shaderScript = document.getElementById(source);
    if (shaderScript)
        source = shaderScript.text;
    var shaderObj = gl.createShader(shaderStage);
    gl.shaderSource(shaderObj, source);
    gl.compileShader(shaderObj);
    var status = gl.getShaderParameter(shaderObj, gl.COMPILE_STATUS);
    if (!status) alert(gl.getShaderInfoLog(shaderObj));
    return status ? shaderObj : null;
},
Link: function (shaderObjs) {
    var prog = gl.createProgram();
    for (var i_sh = 0; i_sh < shaderObjs.length; ++i_sh)
        gl.attachShader(prog, shaderObjs[i_sh]);
    gl.linkProgram(prog);
    status = gl.getProgramParameter(prog, gl.LINK_STATUS);
    if ( !status ) alert(gl.getProgramInfoLog(prog));
    return status ? prog : null;
} };

var VertexBuffer = {
Create: function(attribs, indices, type) {
    var buffer = { buf: [], attr: [], inx: gl.createBuffer(), inxLen: indices.length, primitive_type: type ? type : gl.TRIANGLES };
    for (var i=0; i<attribs.length; ++i) {
        buffer.buf.push(gl.createBuffer());
        buffer.attr.push({ size : attribs[i].attrSize, loc : attribs[i].attrLoc, no_of: attribs[i].data.length/attribs[i].attrSize });
        gl.bindBuffer(gl.ARRAY_BUFFER, buffer.buf[i]);
        gl.bufferData(gl.ARRAY_BUFFER, new Float32Array( attribs[i].data ), gl.STATIC_DRAW);
    }
    gl.bindBuffer(gl.ARRAY_BUFFER, null);
    if ( buffer.inxLen > 0 ) {
        gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, buffer.inx);
        gl.bufferData(gl.ELEMENT_ARRAY_BUFFER, new Uint16Array( indices ), gl.STATIC_DRAW);
        gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, null);
    }
    return buffer;
},
Draw: function(bufObj) {
    for (var i=0; i<bufObj.buf.length; ++i) {
        gl.bindBuffer(gl.ARRAY_BUFFER, bufObj.buf[i]);
        gl.vertexAttribPointer(bufObj.attr[i].loc, bufObj.attr[i].size, gl.FLOAT, false, 0, 0);
        gl.enableVertexAttribArray( bufObj.attr[i].loc);
    }
    if ( bufObj.inxLen > 0 ) {
        gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, bufObj.inx);
        gl.drawElements(bufObj.primitive_type, bufObj.inxLen, gl.UNSIGNED_SHORT, 0);
        gl.bindBuffer( gl.ELEMENT_ARRAY_BUFFER, null );
    }
    else
        gl.drawArrays(bufObj.primitive_type, 0, bufObj.attr[0].no_of );
    for (var i=0; i<bufObj.buf.length; ++i)
        gl.disableVertexAttribArray(bufObj.attr[i].loc);
    gl.bindBuffer( gl.ARRAY_BUFFER, null );
} };

var Texture = {};
Texture.HandleLoadedTexture2D = function( image, texture, flipY ) {
    gl.activeTexture( gl.TEXTURE0 );
    gl.bindTexture( gl.TEXTURE_2D, texture );
    gl.pixelStorei( gl.UNPACK_FLIP_Y_WEBGL, flipY != undefined && flipY == true );
    gl.texImage2D( gl.TEXTURE_2D, 0, gl.RGBA, gl.RGBA, gl.UNSIGNED_BYTE, image );
    gl.texParameteri( gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.LINEAR );
    gl.texParameteri( gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR );
    gl.texParameteri( gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.REPEAT );
  	gl.texParameteri( gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.REPEAT );
    gl.bindTexture( gl.TEXTURE_2D, null );
    return texture;
}
Texture.LoadTexture2D = function( name ) {
    var texture = gl.createTexture();
    texture.image = new Image();
    texture.image.setAttribute('crossorigin', 'anonymous');
    texture.image.onload = function () {
        Texture.HandleLoadedTexture2D( texture.image, texture, false )
    }
    texture.image.src = name;
    return texture;
}

initScene();

})();

html,body { margin: 0; overflow: hidden; }
#gui-left { position : absolute; top : 0; left : 0; color: #40f040; }

<script id="draw-shader-vs" type="x-shader/x-vertex">
    precision mediump float;

    attribute vec2 inPos;
    varying   vec2 vertPos;
    uniform   vec2 u_vp_size;

    void main()
    {
        vec2 scale  = u_vp_size.x > u_vp_size.y ? vec2(u_vp_size.y/u_vp_size.x, 1.0) : vec2(1.0, u_vp_size.x/u_vp_size.y);
        vertPos     = inPos;
        gl_Position = vec4( inPos * scale, 0.0, 1.0 );
    }
</script>

<script id="draw-shader-fs" type="x-shader/x-fragment">
    precision mediump float;

    varying vec2      vertPos;
    uniform sampler2D u_texture;
    uniform float     u_saturate;

    const float Epsilon = 1e-10;
 
    vec3 RGBtoHSV(in vec3 RGB)
    {
        vec4  P   = (RGB.g < RGB.b) ? vec4(RGB.bg, -1.0, 2.0/3.0) : vec4(RGB.gb, 0.0, -1.0/3.0);
        vec4  Q   = (RGB.r < P.x) ? vec4(P.xyw, RGB.r) : vec4(RGB.r, P.yzx);
        float C   = Q.x - min(Q.w, Q.y);
        float H   = abs((Q.w - Q.y) / (6.0 * C + Epsilon) + Q.z);
        vec3  HCV = vec3(H, C, Q.x);
        float S   = HCV.y / (HCV.z + Epsilon);
        return vec3(HCV.x, S, HCV.z);
    }

    vec3 HSVtoRGB(in vec3 HSV)
    {
        float H   = HSV.x;
        float R   = abs(H * 6.0 - 3.0) - 1.0;
        float G   = 2.0 - abs(H * 6.0 - 2.0);
        float B   = 2.0 - abs(H * 6.0 - 4.0);
        vec3  RGB = clamp( vec3(R,G,B), 0.0, 1.0 );
        return ((RGB - 1.0) * HSV.y + 1.0) * HSV.z;
    }
    
    void main()
    {
        vec2 texCoord = vec2( vertPos.s, -vertPos.t ) * 0.5 + 0.5;
        vec3 texColor = texture2D( u_texture, texCoord.st ).rgb;

        vec3 col_hsv = RGBtoHSV(texColor.rgb);
        col_hsv.y *= (u_saturate * 2.0); 
        vec3 col_rgb = HSVtoRGB(col_hsv.rgb);

        gl_FragColor  = vec4( col_rgb.rgb, 1.0 );
    }
</script>

<div id="gui-left">
  <table>
  <tr><td>saturate</td><td><input type="range" id="saturate" min="0" max="100" value="50"/></td></tr>
  </table>
</div>

<canvas id="texture-canvas" style="border: none"></canvas>

在着色器代码中增加纹理的强度-OpenGL

2 个答案: