C++ 创建图像
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C++ creating image
提问by Adam
I haven't been programming in C++ for a while, and now I have to write a simple thing, but it's driving me nuts.
我有一段时间没有用 C++ 编程，现在我必须写一个简单的东西，但这让我发疯。
I need to create a bitmap from a table of colors:
char image[200][200][3];
我需要从颜色表创建位图：
char image[200][200][3];
First coordinate is width, second height, third colors: RGB. How to do it?
第一个坐标是宽度，第二个高度，第三个颜色：RGB。怎么做？
Thanks for any help. Adam
谢谢你的帮助。亚当
回答by Ron Warholic
I'm sure you've already checked http://en.wikipedia.org/wiki/BMP_file_format.
我确定您已经检查过http://en.wikipedia.org/wiki/BMP_file_format。
With that information in hand we can write a quick BMP with:
有了这些信息，我们可以编写一个快速的 BMP：
// setup header structs bmpfile_header and bmp_dib_v3_header before this (see wiki)
// * note for a windows bitmap you want a negative height if you're starting from the top *
// * otherwise the image data is expected to go from bottom to top *
FILE * fp = fopen ("file.bmp", "wb");
fwrite(bmpfile_header, sizeof(bmpfile_header), 1, fp);
fwrite(bmp_dib_v3_header, sizeof(bmp_dib_v3_header_t), 1, fp);
for (int i = 0; i < 200; i++) {
for (int j = 0; j < 200; j++) {
fwrite(&image[j][i][2], 1, 1, fp);
fwrite(&image[j][i][1], 1, 1, fp);
fwrite(&image[j][i][0], 1, 1, fp);
}
}
fclose(fp);
If setting up the headers is a problem let us know.
如果设置标题有问题，请告诉我们。
Edit: I forgot, BMP files expect BGR instead of RGB, I've updated the code (surprised nobody caught it).
编辑：我忘了，BMP 文件需要 BGR 而不是 RGB，我已经更新了代码（很惊讶没有人发现它）。
回答by dagoof
I'd suggest ImageMagick, comprehensive library etc.
我建议使用ImageMagick、综合库等。
回答by Jaime Ivan Cervantes
For simple image operations I highly recommend Cimg. This library works like a charm, and is extremely easy to use. You just have to include a header file in your code. It literally took me less than 10 minutes to compile and test.
对于简单的图像操作，我强烈推荐Cimg。这个库就像一个魅力，非常容易使用。您只需要在代码中包含一个头文件。从字面上看，我花了不到 10 分钟的时间来编译和测试。
If you want to do more complicated image operations however, I would go with Magick++as suggested by dagoof.
但是，如果您想做更复杂的图像操作，我会按照 dagoof 的建议使用Magick++。
回答by Igor Oks
I would first try to find out, how the BMP file format(that's what you mean by a bitmap, right?) is defined. Then I would convert the array to that format and print it to the file.
我将首先尝试找出BMP 文件格式（这就是位图的意思，对吧？）是如何定义的。然后我会将数组转换为该格式并将其打印到文件中。
If that's an option, I would also consider trying to find an existing library for BMP files creation, and just use it.
如果这是一个选项，我还会考虑尝试查找用于创建 BMP 文件的现有库，然后使用它。
Sorry if what I said is already obvious for you, but I don't know on which stage of the process you are stuck.
对不起，如果我说的对你来说已经很明显了，但我不知道你卡在了流程的哪个阶段。
回答by Goz
It would be advisable to initialise the function as a simple 1 dimensional array.
建议将函数初始化为简单的一维数组。
ie (Where bytes is the number of bytes per pixel)
即（其中字节是每个像素的字节数）
char image[width * height * bytes];
You can then access the relevant position in the array as follows
然后可以按如下方式访问数组中的相关位置
char byte1 = image[(x * 3) + (y * (width * bytes)) + 0];
char byte2 = image[(x * 3) + (y * (width * bytes)) + 1];
char byte3 = image[(x * 3) + (y * (width * bytes)) + 2];
