Update lec11

README.md

@@ -1515,3 +1515,108 @@ int main()
         fprintf(stdout, "%d + %d : %d \n", ia, ib, ic);
 }
 ```
+
+## **Lecture 11**
+
+### rgba.c 코드
+```
+#include <stdio.h>
+
+typedef unsigned int t_rgba;
+
+// input value must be 0~255
+
+/*
+방법 1. 함수 만들기
+unsigned int fromRGBA(int r, int g, int b, int a)
+{
+
+        if (r > 255 || r < 0)
+                r = 0;
+        if (g > 255 || g < 0)
+                g = 0;
+        if (b > 255 || b < 0)
+                b = 0;
+        if (a > 255 || a < 0)
+                a = 0;
+        if문 성능 나빠짐
+
+
+        // return r*256*256*256 + g*256*256 + b*256 + a*1;
+        // return ((r<<24)+(g<<16)+(b<<8)+a);
+        // return ((r<<(24+g))<<(16+b))<<(8+1);
+        // return (r<<24|g<<16|b<<8|a);
+        return ((r&0xff)<<24)|((g&0xff)<<16)|((b&0xff)<<8)|(a&0xff);
+}
+*/
+
+// 방법 2. macro
+#define fromRGBA(r,g,b,a) ((((r)&0xff)<<24)|(((g)&0xff)<<16)|(((b)&0xff)<<8)|((a)&0xff))
+#define F_NUM_1_255       (1.0f/255.0f)
+
+t_rgba mul_float(t_rgba c1, t_rgba c2){
+        float r1, g1, b1, a1;
+        float r2, g2, b2, a2;
+        int   ir, ig, ib, ia;
+
+        r1 = (float) ((c1 >> 24) & 0xff) * F_NUM_1_255;
+        g1 = (float) ((c1 >> 16) & 0xff) * F_NUM_1_255;
+        b1 = (float) ((c1 >>  8) & 0xff) * F_NUM_1_255;
+        a1 = (float) ((c1 >>  0) & 0xff) * F_NUM_1_255;
+
+        r2 = (float) ((c2 >> 24) & 0xff) * F_NUM_1_255;
+        g2 = (float) ((c2 >> 16) & 0xff) * F_NUM_1_255;
+        b2 = (float) ((c2 >>  8) & 0xff) * F_NUM_1_255;
+        a2 = (float) ((c2 >>  0) & 0xff) * F_NUM_1_255;
+
+        ir = (int) ((r1 * r2) * 255.0f);
+        ig = (int) ((g1 * g2) * 255.0f);
+        ib = (int) ((b1 * b2) * 255.0f);
+        ia = (int) ((a1 * a2) * 255.0f);
+
+        return fromRGBA(ir, ig, ib, ia);
+}
+
+t_rgba mul_int(t_rgba c1, t_rgba c2)
+{
+        unsigned int r1, g1, b1, a1;
+        unsigned int r2, g2, b2, a2;
+        unsigned int  r,  g,  b,  a;
+
+        r1 =  c1 >> 24         ; r2 =  c2 >> 24        ;
+        g1 = (c1 >> 16) & 0xff ; g2 = (c2 >> 16) & 0xff;
+        b1 = (c1 >> 16) & 0xff ; b2 = (c2 >>  8) & 0xff;
+        a1 =  c1        & 0xff ; a2 =  c2        & 0xff;
+
+        r= (r1 * r2) / 255;
+        g= (g1 * g2) / 255;
+        b= (b1 * b2) / 255;
+        a= (a1 * a2) / 255;
+
+        return fromRGBA(r,g,b,a);
+
+}
+
+int main()
+{
+        int red, green, blue, alpha;
+        t_rgba rgba_1, rgba_2, rgba_3;
+        // input value must be 0~255 : 0.0~1.0
+        // rgba_1 [rrrrrrrr][gggggggg][bbbbbbbb][aaaaaaaa]
+        printf("input 4 values with 0~255 : ");
+        scanf("%d %d %d %d", &red, &green, &blue, &alpha);
+        rgba_1 = fromRGBA(red, green, blue, alpha);
+        printf("%d %d %d %d : %u 0x%08x\n", red, green, blue, alpha, rgba_1, rgba_1);
+        rgba_2 = mul_float(rgba_1, rgba_1);
+        printf("%d %d %d %d : %u 0x%08x\n", red, green, blue, alpha, rgba_2, rgba_2);
+        rgba_3 = mul_int(rgba_1, rgba_1);
+        printf("%d %d %d %d : %u 0x%08x\n", red, green, blue, alpha, rgba_3, rgba_3);
+}
+```
+출력 결과
+```
+input 4 values with 0~255 : 127 127 127 127
+127 127 127 127 : 2139062143 0x7f7f7f7f
+127 127 127 127 : 1061109567 0x3f3f3f3f
+127 127 127 127 : 1061109567 0x3f3f3f3f
+```