掃描的PDF頁面是斜的，用軟件自動糾偏效果很差，於是想到了之前的方法：
- 先deflate手裏的pdf；
- 然後找到圖片對應的頁面
- 添加q...Q行，然後在其中間添加cm命令，控制圖像本身。
% 25 0 obj
% << /Length 107 >>
% stream
q
0.480000 0 0 0.480000 0 0 cm
1 -0.01 0 1 0 0 cm % page 5
1240 0 0 1753 0 0 cm
/Im5 Do
Q
% endstream
| 命令 | 解釋 |
|---|---|
| 1 -0.01 0 1 0 0 cm % page 5 | transformation matrices(CTM) |
| q,Q,cm | special graphics state |
- Translations are specified as [1 0 0 1 tx ty ], where tx and ty are the distances
to translate the origin of the coordinate system in the horizontal and vertical
dimensions, respectively.- Scaling is obtained by [sx 0 0 sy 0 0]. This scales the coordinates so that 1
unit in the horizontal and vertical dimensions of the new coordinate system is
the same size as sx and sy units, respectively, in the previous coordinate system.- Rotations are produced by [cosθ sinθ −sinθ cosθ 0 0], which has the effect
of rotating the coordinate system axes by an angleθ counterclockwise.- Skew is specified by [1 tanα tanβ 1 0 0], which skews the x axis by an angleα and the y axis by an angle β.
效果如下：
