This document discusses color representation in App Inventor. It contains the following key points: 1. Colors in App Inventor are represented using the #AARRGGBB format, with values between 0-255 for alpha, red, green, and blue components. 2. It demonstrates how to convert between hexadecimal, decimal, and RGB component representations of colors. 3. It shows an example of calculating the signed long integer that corresponds to a given color in #AARRGGBB format.

1. App Inventor
2011/12/20

2. App Inventor !
•
•
…

3. 14

4. • R G
B R = 160 G = 32 B = 240
• Opacity 255
−6283024
4.2.7 -
http://bit.ly/sisAxa

5. Magic Number…( Д |||)

6. App Inventor
4
1.Opacity #AARRGGBB
2. 256 R
3. 256 G
4. 256 B Opacity=α
5. 168 = 4294967296
6. ( ) App Inventor

7. 256 (1)
• 256 = 162 = 28
• 256 162 = 16
2
• 256 28 =2
8

8. 256 (2)
10 2
102 = 10 2
25 × 102 = 25 × 100 = 2500
25 2 2500

9. • Opacity 255 = (FF)16
• R = 160 = (A0)
16
• G = 32 = (20)
16
• B = 240 = (F0) 16

10. 1.Opacity
Opacity 255 = (FF)16
10 255 16 (FF)16
Opacity= (α value)
0 255

11. 2. 256 R R = 160 = (A0)16
256 (FF)16 × (100)16 = (FF00)16
∵ 256 = (100)16 = 16 2 2
R (FF00)16 (A0)16 = (FFA0)16
2

12. 3. 256 G G = 32 = (20)16
(FFA0)16 × (100)16 = (FFA000)16
(FFA000)16 (20)16 = (FFA020)16
2

13. 4. 256 B B = 240 = (F0)16
(FFA020)16 × (100)16 = (FFA02000)16
(FFA02000)16 (F0)16 = (FFA020F0)16
2
#AARRGGBB 32

14. 5. 168 = 4294967296
168 = 4294967296 = (100000000) 16
(FFA020F0)16 - (100000000) 16
FFA020F0
-) 100000000
FFFFFFFFFFA020F0
…

15. (borrow)
65
10
100000000FFA020F0 10
-)0000000100000000 -) 1
FFFFFFFFFFA020F0 F
∵(10)16 - (1) 16 = (F) 16

16. One-Padding 1
5. 168 = 4294967296
(FFA002F0)16 - (100000000) 16
= (FFFFFFFFFFA020F0)16
#FFFFFFFFAARRGGBB
32 All 1 Padding

17. 6. ( ) App Inventor
(FFFFFFFFFFA020F0)16
64 1 signed long
1
(00000000005FDF10)16 = 6283024
∴ −6283024

18. 2
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•

21. •

22. colorNumber Built-in