使用C ++旋转bmp文件？ [英] rotating a bmp file using C++ ?

问题描述

#include<iostream>
#include<fstream>
#include<string>
using namespace std;

int main()
{
	fstream flower("flower.bmp", ios::in | ios::out | ios::binary);
	int width=686;
	int height=800;
	flower.seekg(18,ios::beg);
	flower.put(height);
	flower.seekg(4);
	flower.put(width);
	
	flower.close();
}

推荐答案

只是交换宽度和高度不会旋转图像。您还需要逐个像素地旋转位图数据。这需要相当多的缓冲处理和数据挖掘。有关如何操作的示例，请查看此处：



为CBitmap添加快速的用户可扩展图像处理支持 [ ^ ]

Just exchanging width and height will not rotate the image. You also need to rotate the bitmap data pixel by pixel. That requires quite a bit of buffer handling and data shoveling. For an example how to do it, look here:

Add fast user-extensible image processing support to CBitmap[^]

我害怕我的建议想一想可能会冒犯你一点，所以我可能要说明这个想法可能意味着什么。



假设你有一些位数据，它告诉你（忘记格式，这是无关紧要的）：

你有

宽度= 3，高度= 2，像素数据123456

这意味着第一行是123，第二行是456：

I was afraid that my suggestion to "think a bit" could possibly offend you a bit, so I probably have to illustrate what this thinking could mean.

Suppose you have some bit data, which tells you (forget the "format", it is irrelevant):
you have
width = 3, height = 2, and pixels data 123456
It means that first line is 123 and the second line is 456:

123
456

如果换宽和高度，你会有

If you swap width and height, you would have

width = 2, height = 3:
12
34
56

但顺时针旋转原始图片90°（您可以将计算机屏幕顺时针旋转90°并查看相同的数字），您会看到什么？显然，

But turn original picture 90° clockwise (you can just turn your computer screen 90° clockwise and look at the same numbers), what will you see? apparently,

41
52
63

和counterclickwise：

and counterclickwise:

36
25
14

最后两张图片是正确的，前一张图片是正确的是腐败的。这里有什么不明显的？

这就是nv3的意思，告诉你逐个像素地旋转位图数据。



我希望现在问题应该清楚了。

-SA

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