//纹理坐标
varying lowp vec2 varyingCoord;
//纹理
uniform sampler2D textureMap;
//色温
uniform lowp float temperature;
//色温过滤器
const lowp vec3 warmFilter =vec3(0.93,0.54,0);
//RGBtoYIQ
const mediump mat3 RGB2YIQ = mat3(0.299, 0.587, 0.114, 0.596, -0.274, -0.322, 0.212, -0.523, 0.311);
//YIQtoRGB
const mediump mat3 YIQ2RGB = mat3(1.0, 0.956, 0.621, 1.0, -0.272, -0.647, 1.0, -1.105, 1.702);
//亮度加权
const mediump vec3 lumanaceWeight = vec3(0.2125,0.7154,0.0721);
void main(){
//读取每个像素点的颜色值
lowp vec4 source = texture2D(textureMap,textureCoordinate);
//源颜色RGB转换为YIQ颜色
mediump vec3 yiq = RGB2YIQ * source.rgb;
/*
clamp(x,minVal,maxVal):裁剪
1.x与minVal比较，取较大值；
2.上一步得到的结果与maxVal比较，取较小值；
yiq.b：b ->指yiq中的第三个值，而不是其b值
*/
yiq.b = clamp(yiq.b,-0.5226,0.5226);
//YIQ颜色转RGB颜色
lowp vec3 rgb = YIQ2RGB * yiq;
/*
色温计算:
warmR:色温h过滤器--warmFilter
if r<0.5 -->2.0*r*warmR;
if r>= 0.5-->1.0-2.0*(1.0-r)*(1.0-warmR);
*/
lowp float A = (rgb.r <0.5? (2.0* rgb.r * warmFilter.r) : (1.0-2.0* (1.0- rgb.r) * (1.0- warmFilter.r)));
lowp float B = (rgb.g <0.5? (2.0* rgb.g * warmFilter.g) : (1.0-2.0* (1.0- rgb.g) * (1.0- warmFilter.g)));
lowp float C = (rgb.b <0.5? (2.0* rgb.b * warmFilter.b) : (1.0-2.0* (1.0- rgb.b) * (1.0- warmFilter.b)));
//组件新的颜色值
lowp vec3 color =vec3(A,B,C);
/*
mix(x,y,a):将颜色与颜色/纹理与纹理/纹理与颜色通过线性方程式混合
方程式：x.(1-a)+y.a --> vec3向量颜色
vec4(vec3,w);-->vec4向量
*/
gl_FragColor = vec4(mix(rgb,color，temperature),source.a);
}
