1
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Ok, daar gaan we.
2
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Dit is een bijzonder moment,
3
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want we gaan nu echt regels code schrijven.
4
00:00:08,799 --> 00:00:10,799
Maar wat is een regel code eigenlijk?
5
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Het is een opdracht aan de computer
6
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Met welke zullen we beginnen?
7
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We beginnen met "teken een rechthoek".
8
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Hoe laat je de computer dit doen?
9
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De computer spreekt een andere taal
10
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dus je gebruikt andere andere woorden.
11
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In dit geval schrijf je "rect".
12
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rect wordt ook wel een "functie" genoemd.
13
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De functie van rect is rechthoeken tekenen.
14
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We moeten nu nog iets specifieker worden
15
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Hoe hoog en hoe breed,
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en waar op het scherm
17
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willen we de rechthoek precies plaatsen?
18
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dit zijn dingen die de computer
19
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heel precies wil weten.
20
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Laten we beginnen met de plek
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op het scherm. Hoe kun je dingen
22
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daar eigenlijk op plaatsen?
23
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Het scherm voor je neus
24
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is zelf ook een rechthoek.
25
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Net als bij schilderen noemen we
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dit oppervlak het "canvas".
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Net als bij schaken is er een systeem
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van coordinaten. We kunnen bijvoorbeeld
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zeggen dat de linker bovenhoek
30
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op punt 16,23 moet beginnen.
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Je geeft dingen een plek
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op de horizontale (x) of verticale (y) as.
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OK, dit is 0, 1 ,2 ,3 ,4, 5, 6, 7, 8, 9
34
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Dus deze zou bij "pixel" 9 beginnen.
35
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Wat bedoel ik met pixel ?
36
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Zoals we in het dagelijks leven centimers
37
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of kilometers hebben, zo meet je afstand op
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computerscherm in pixels.
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Elke pixel is een gekleurd puntje op het
40
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beeldscherm. Dit venster heeft een breedte
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en hoogte in pixels. In deze cursus zal
42
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het venster 500 bij 400 pixels zijn.
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Dus als het venster 500 pixels breed is,
44
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hoeveel pixels is het tot het midden? 250!
45
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En waar zit dan verticaal het midden?
46
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Inderdaad, op 200 pixels!
47
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Door aan de rect functie coordinaten
48
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toe te voegen, vertellen we de computer
49
00:02:56,178 --> 00:03:00,052
hoe we de rechthoek willen.
50
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Coordinaten plaatsen we tussen haakjes,
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en elke regel eindigen we
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met een punt-komma. Dat ziet er
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dan zo uit.
54
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In het midden plaatsen we dedetails:
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de coordinaten, de breedte en hoogte.
56
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De coordinaten wijzen de
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linker-bovenhoek van de rechthoek aan.
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De X en Y positie: x = 250, y = 200.
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250, 200
60
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Ook de breedte en hoogte geven we aan.
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Eerst de breedte.
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Laten we 'm 150 bred en 100 hoog maken.
63
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We hebben nu vier getallen ingevuld.
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Dit is een bijzonder moment:
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je eerste regel computercode ooit
66
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staat nu op het scherm!
67
00:04:05,750 --> 00:04:10,205
Het is een functie met vier "argumenten".
68
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Waar is de rechthoek?
69
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70
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71
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72
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73
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74
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75
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76
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77
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78
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79
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80
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81
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82
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83
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84
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85
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86
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87
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88
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89
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90
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91
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92
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93
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94
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95
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96
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97
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98
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99
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100
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101
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102
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103
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104
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105
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106
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107
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108
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109
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110
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111
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112
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113
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114
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115
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116
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117
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119
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120
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122
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125
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126
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127
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128
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129
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130
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131
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132
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133
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134
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135
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136
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137
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138
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139
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140
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141
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142
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143
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144
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145
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146
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147
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148
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149
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150
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151
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152
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153
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154
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155
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156
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157
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158
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159
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160
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161
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162
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163
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164
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165
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166
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167
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168
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169
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170
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171
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172
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173
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174
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175
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176
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