November 2018
Intermediate to advanced
272 pages
6h 51m
Japanese
book
エレガントなSciPy ―Pythonによる科学技術計算
by Juan Nunez-Iglesias, Stéfan van der Walt, Harriet Dashnow, 山崎 邦子, 山崎 康宏
Content preview from エレガントなSciPy ―Pythonによる科学技術計算
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129
5.3 疎行列の適用例：画像変換
思った通りに回転しましたね。
5.3.1
演習：画像の回転
回転は、原点すなわち座標
(0, 0)
を中心に行われます。では、画像中央を中心とした回転はでき
るでしょうか。
平行移動
（つまり画像を上下左右にスライドさせる）のための変換行列は、以下のように与えられ
ます。
H
tr
=
1 0 t
r
0 1 t
c
0 0 1
これは、画像を
t
r
ピクセル下に、
t
c
ピクセル右に動かしたい場合です。
すでに述べましたが、画像変換に疎な線形演算子を使う手法は、高速です。性能を
ndimage
と比
図
5-3
疎演算子を使って画像を回転する
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