如何在 C++ 中将 RGB 颜色值转换为十六进制值？
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how to convert a RGB color value to an hexadecimal value in C++?
提问by Tahlil
In my C++ application, I have a png image's color in terms of Red, Green, Blue values. I have stored these values in three integers.
在我的 C++ 应用程序中，我有一个 png 图像的颜色，即红、绿、蓝值。我已将这些值存储在三个整数中。
How to convert RGB values into the equivalent hexadecimal value?
如何将RGB值转换为等效的十六进制值？
Example of that like in this format 0x1906
类似这种格式的示例 0x1906
EDIT: I will save the format as GLuint.
编辑：我将格式保存为 GLuint。
回答by Nikos C.
Store the appropriate bits of each color into an unsigned integer of at least 24 bits (like a long):
将每种颜色的适当位存储为至少 24 位的无符号整数（如 a long）：
unsigned long createRGB(int r, int g, int b)
{
return ((r & 0xff) << 16) + ((g & 0xff) << 8) + (b & 0xff);
}
Now instead of:
现在代替：
unsigned long rgb = 0xFA09CA;
you can do:
你可以做：
unsigned long rgb = createRGB(0xFA, 0x09, 0xCA);
Note that the above will not deal with the alpha channel. If you need to also encode alpha (RGBA), then you need this instead:
请注意，以上内容不会处理 alpha 通道。如果你还需要编码 alpha (RGBA)，那么你需要这个：
unsigned long createRGBA(int r, int g, int b, int a)
{
return ((r & 0xff) << 24) + ((g & 0xff) << 16) + ((b & 0xff) << 8)
+ (a & 0xff);
}
Replace unsigned longwith GLuintif that's what you need.
如果您需要，请替换unsigned long为GLuint。
回答by unwind
If you want to build a string, you can probably use snprintf():
如果你想建立一个字符串，你可能可以使用snprintf()：
const unsigned red = 0, green = 0x19, blue = 0x06;
char hexcol[16];
snprintf(hexcol, sizeof hexcol, "%02x%02x%02x", red, green, blue);
This will build the string 001906" inhexcol`, which is how I chose to interpret your example color (which is only four digits when it should be six).
这将构建字符串001906" inhexcol`，这就是我选择解释您的示例颜色的方式（它应该是六位时只有四位数字）。
You seem to be confused over the fact that the GL_ALPHApreprocessor symbol is defined to be 0x1906in OpenGL's header files. This is not a color, it's a format specifierused with OpenGL API calls that deal with pixels, so they know what format to expect.
您似乎对GL_ALPHA预处理器符号被定义0x1906在 OpenGL 的头文件中这一事实感到困惑。这不是颜色，它是与处理像素的 OpenGL API 调用一起使用的格式说明符，因此它们知道期望什么格式。
If you have a PNG image in memory, the GL_ALPHAformat would correspond to onlythe alpha values in the image (if present), the above is something totally different since it builds a string. OpenGL won't need a string, it will need an in-memory buffer holding the data in the format required.
如果内存中有 PNG 图像，则GL_ALPHA格式将仅对应于图像中的 alpha 值（如果存在），上面的内容完全不同，因为它构建了一个字符串。OpenGL 不需要字符串，它需要一个内存缓冲区，以所需的格式保存数据。
See the glTexImage2D()manual page for a discussion on how this works.
有关其glTexImage2D()工作原理的讨论，请参阅手册页。
