Question

我正在尝试使用LUT将色阶着色器实现为here by Matt DesLauriers和here by Lev Zelensky所述的处理，但是当我将着色器与标准lut一起应用时，会得到一个奇怪的结果：

在左侧，您可以看到应用LUT着色器时获得的结果，而在右侧则是所需的结果。

这是我在处理中的实现：

PImage source;
PShader PP_LUT;
PGraphics buffer;
PGraphics lut;
PImage lutsrc;

void setup() {
  size(512, 512), P2D);
  source = loadImage("test.png");
  lutsrc = loadImage("_LUT/lookup.png");

  lut = createGraphics(lutsrc.width, lutsrc.height, P2D);
  ((PGraphicsOpenGL)lut).textureSampling(2);

  lut.beginDraw();
  lut.image(lutsrc, 0, 0);
  lut.endDraw();

  buffer = createGraphics(source.width, source.height, P3D);

  PP_LUT = loadShader("PP_LUT.glsl");
  PP_LUT.set("resolution", (float) buffer.width, (float) buffer.height);  
  PP_LUT.set("lut", lut);
}

void draw() {
  buffer.beginDraw();
  buffer.background(0);
  buffer.shader(PP_LUT);
  buffer.image(source, 0, 0);
  buffer.endDraw();

  image(buffer, 0, 0, width, height);
  image(lut, 0, 0, width * 0.25, height * 0.25);
}

和着色器部分：

#version 150
#ifdef GL_ES
#endif

uniform sampler2D texture;
uniform sampler2D lut;

in vec4 vertTexCoord;
out vec4 fragColor;

//https://github.com/mattdesl/glsl-lut
vec4 lookup(vec4 color_, sampler2D lut_){
    color_ = clamp(color_, vec4(0), vec4(1));
    //define blue
    mediump float blue = color_.b * 63.0;

    //define quad 1
    mediump vec2 quaduv1;
    quaduv1.y = floor(floor(blue) / 8.0); //devide blue by the number of col on the LUT
    quaduv1.x = floor(blue) - (quaduv1.y * 8.0); 

    //define quad 2
    mediump vec2 quaduv2;
    quaduv2.y = floor(ceil(blue) / 8.0); //devide blue by the number of col on the LUT
    quaduv2.x = ceil(blue) - (quaduv2.y * 8.0); 

    //define colorUV 1 
    highp vec2 coloruv1;
    coloruv1.x = (quaduv1.x * 0.125) + 0.5/512.0 + ((0.125 - 1.0/512.0) * color_.r);
    coloruv1.y = (quaduv1.y * 0.125) + 0.5/512.0 + ((0.125 - 1.0/512.0) * color_.g);

    //define colorUV 2
    highp vec2 coloruv2;
    coloruv2.x = (quaduv2.x * 0.125) + 0.5/512.0 + ((0.125 - 1.0/512.0) * color_.r);
    coloruv2.y = (quaduv2.y * 0.125) + 0.5/512.0 + ((0.125 - 1.0/512.0) * color_.g);

    //PROCESSING NEED TO FLIP y uv
    //coloruv1.y = 1.0 - coloruv1.y;
    //coloruv2.y = 1.0 - coloruv2.y;

    //define new color 1 & 2
    lowp vec4 ncolor1 = texture2D(lut_, coloruv1);
    lowp vec4 ncolor2 = texture2D(lut_, coloruv2);

    //return looked up color
    lowp vec4 lookedcolor = mix(ncolor1, ncolor2, fract(blue));
    return vec4(lookedcolor.rgb, color_.w); 
}

void main()
{
    vec2 uv = vertTexCoord.xy;
    vec4 color = texture2D(texture, uv);
    vec4 lutColor = lookup(color, lut);

    fragColor = lutColor;
}

据我了解，纹理过滤部分似乎存在问题，因此我尝试将lut写入屏幕外缓冲区，并按照the wiki page of processing所述将纹理过滤模式设置为最近，但结果是一样

我不知道我在这里想念的是什么。谁能对此有个想法？

谢谢

使用LUT和PShader进行颜色分级

0 个答案: