深入iOS開發 iOS仿射變換和3D變換

2d仿射變換

uiview的transform屬性是乙個cgaffinetransform型別，用於在二維空間做旋轉，縮放和平移。cgaffinetransform是乙個可以和二維空間向量（例如cgpoint）做乘法的3x2的矩陣:

1240

paste_image.png

當對uiview應用變換矩陣，uiview圖層矩形內的每乙個點都被相應地做變換，從而形成乙個新的四邊形的形狀。cgaffinetransform中的「仿射」的意思是無論變換矩陣用什麼值，圖層中平行的兩條線在變換之後任然保持平行.

單位矩陣

cgaffinetransformidentity

cgaffinetransform transform = cgaffinetransformidentity;

結果:(cgaffinetransform) transform = (a = 1, b = 0, c = 0, d = 1, tx = 0, ty = 0)

建立仿射變換矩陣

cgaffinetransformmakerotation(cgfloat angle) // 旋轉

cgaffinetransformmakescale(cgfloat sx, cgfloat sy) // 縮放

cgaffinetransformmaketranslation(cgfloat tx, cgfloat ty) // 平移

cgaffinetransform transform = cgaffinetransformmakerotation(m_pi_4);

結果 :

(cgaffinetransform) transform = (a = 0.70710678118654757, b = 0.70710678118654746, c = -0.70710678118654746, d = 0.70710678118654757, tx = 0, ty = 0)

cgaffinetransform transform = cgaffinetransformmakescale(0.8, 0.8);

結果：(cgaffinetransform) transform = (a = 0.80000000000000004, b = 0, c = 0, d = 0.80000000000000004, tx = 0, ty = 0)

cgaffinetransform transform = cgaffinetransformmaketranslation(10, 10);

結果：(cgaffinetransform) transform = (a = 1, b = 0, c = 0, d = 1, tx = 10, ty = 10)

1240

paste_image.png

圖中，灰色為舊圖，藍色為變化後的新圖.