什么是Core Image Kernel Language中的texture（iChannel0，vec2）等效项？

Question

float r = texture(iChannel3, view1).r;
float g = texture(iChannel3, view2).g;
float b = texture(iChannel3, view3).b;

fragColor = vec4(r, g, b, 1.);

如何在Core Image Kernel Language中转换此着色器语法？