将位图变灰色的函数

#include <windows.h>

// 将位图变灰色的函数

void MakeBitmapGrayscale(HBITMAP hBitmap) {

BITMAP bm;

GetObject(hBitmap, sizeof(BITMAP), &bm);

int width = bm.bmWidth;

int height = bm.bmHeight;

int lineBytes = bm.bmWidthBytes;

BYTE *pixels = new BYTE[lineBytes * height];

HDC hDC = GetDC(NULL);

HDC hMemDc = CreateCompatibleDC(hDC);

HBITMAP hOldBitmap = (HBITMAP)SelectObject(hMemDc, hBitmap);

GetBitmapBits(hBitmap, lineBytes * height, pixels);

for (int i = 0; i < height; ++i) {

for (int j = 0; j < width; ++j) {

BYTE *pixel = pixels + i * lineBytes + j * 4;

// 计算灰色值

BYTE gray = (pixel[2] + pixel[1] + pixel[0]) / 3;

// 设置RGB通道的值为灰色值

pixel[0] = gray;

pixel[1] = gray;

pixel[2] = gray;

}

}

SetBitmapBits(hBitmap, lineBytes * height, pixels);

SelectObject(hMemDc, hOldBitmap);

DeleteDC(hMemDc);

ReleaseDC(NULL, hDC);

delete[] pixels;

}

原文地址：https://blog.csdn.net/asmfox/article/details/140695006

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