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截圖：繪製HSL的SL圈調色板
正如你可以看到上面的PIC，我創建了HSL調色板在iOS和我繪製的OpenGL着色器核心部分，但它是正確的，我們可以使它成爲一個圓圈，而不是作物，我們需要將所有顏色繪製成一個圓圈？我試了很久，但都失敗了。你可以幫我嗎？非常感謝！
下面是代碼：
- (void)loadShaders {
// create shader program
program = glCreateProgram();
const GLchar *vertexProgram = "precision highp float; \n\
\n\
attribute vec4 position; \n\
varying vec2 uv; \n\
\n\
void main() \n\
{ \n\
gl_Position = vec4(2.0 * position.x - 1.0, 2.0 * position.y - 1.0, 0.0, 1.0); \n\
uv = position.xy; \n\
}";
GLuint vertexShader = glCreateShader(GL_VERTEX_SHADER);
glShaderSource(vertexShader, 1, &vertexProgram, NULL);
glCompileShader(vertexShader);
glAttachShader(program, vertexShader);
// https://gist.github.com/eieio/4109795
const GLchar *fragmentProgram = "precision highp float; \n\
varying vec2 uv; \n\
uniform float hue; \n\
vec3 hsb_to_rgb(float h, float s, float l) \n\
{ \n\
float c = l * s; \n\
h = mod((h * 6.0), 6.0); \n\
float x = c * (1.0 - abs(mod(h, 2.0) - 1.0)); \n\
vec3 result; \n\
\n\
if (0.0 <= h && h < 1.0) { \n\
result = vec3(c, x, 0.0); \n\
} else if (1.0 <= h && h < 2.0) { \n\
result = vec3(x, c, 0.0); \n\
} else if (2.0 <= h && h < 3.0) { \n\
result = vec3(0.0, c, x); \n\
} else if (3.0 <= h && h < 4.0) { \n\
result = vec3(0.0, x, c); \n\
} else if (4.0 <= h && h < 5.0) { \n\
result = vec3(x, 0.0, c); \n\
} else if (5.0 <= h && h < 6.0) { \n\
result = vec3(c, 0.0, x); \n\
} else { \n\
result = vec3(0.0, 0.0, 0.0); \n\
} \n\
\n\
result.rgb += l - c; \n\
\n\
return result; \n\
} \n\
\n\
void main() \n\
{ \
gl_FragColor = vec4(hsb_to_rgb(hue, uv.x, uv.y), 1.0); \
}";
GLuint fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
glShaderSource(fragmentShader, 1, &fragmentProgram, NULL);
glCompileShader(fragmentShader);
glAttachShader(program, fragmentShader);
// bind attribute locations
// this needs to be done prior to linking
glBindAttribLocation(program, ATTRIB_VERTEX, "position");
glLinkProgram(program);
glDeleteShader(vertexShader);
glDeleteShader(fragmentShader);
}