英文:
Flip image vertically in C++ without external libraries like OpenCV
问题
我有以下的函数，它接收void*类型的图像数据。如何在不使用像OpenCV这样的外部库的情况下将其上下翻转？已知图像的宽度和高度。
注意：这个函数将在Android上以每秒至少30次的频率调用，所以需要高效的解决方案。
PushVideoFrame(void *bytes, int width, int height) {
if (clientPtr == nullptr) {
return ErrorCodes::DEVICE_CONNECTION;
}
char* data = static_cast<char*>(bytes);
//////// 翻转图像的代码 /////////////
clientPtr->PushVideoFrameAsync(data, width * height * 4);
}
英文:
I have the following function which receives image as void*. How can I flip it upside down without using external libraries like OpenCV. Image width and height are known.
Note: this function will be called at least 30 times a second on Android so this needs to be efficient.
PushVideoFrame(void *bytes, int width, int height) {
if (clientPtr == nullptr) {
return ErrorCodes::DEVICE_CONNECTION;
}
char* data = static_cast< char *>(bytes);
//////// CODE TO FLIP IMAGE /////////////
clientPtr->PushVideoFrameAsync(data, width * height * 4)
}
答案1
得分: 0
你可以使用额外内存来交换行：
void flipVertically(uint8_t *data, int width, int height) {
vector<uint8_t> temp(width);
for (int i = 0; i < height / 2; i++) {
void *ptr1 = data + i * width;
void *ptr2 = data + (height - i - 1) * width;
// 使用临时缓冲区交换（行1，行2）
memcpy(&temp[0], ptr1, width);
memcpy(ptr1, ptr2, width);
memcpy(ptr2, &temp[0], width);
}
}
这段代码用于垂直翻转图像数据的行。
英文:
You can swap rows with additional memory:
void flipVertically(uint8_t *data, int width, int height) {
vector<uint8_t> temp(width);
for (int i = 0; i < height / 2; i++) {
void *ptr1 = data + i*width;
void *ptr2 = data + (height-i-1)*width;
// swap(row1, row2) with temp buffer
memcpy(&temp[0], ptr1, width);
memcpy(ptr1, ptr2, width);
memcpy(ptr2, &temp[0], width);
}
}
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