这是我过去两天用来调试的代码:
#include <windows.h>
HBITMAP createImageMask(HBITMAP bitmapHandle, const COLORREF transparencyColor) {
// For getting information about the bitmap's height and width in this context
BITMAP bitmap;
// Create the device contexts for the bitmap and its mask
HDC bitmapGraphicsDeviceContext = CreateCompatibleDC(NULL);
HDC bitmapMaskGraphicsDeviceContext = CreateCompatibleDC(NULL);
// For the device contexts to re-select the initial object they initialized with
// and de-select the bitmap and mask
HGDIOBJ bitmapDummyObject;
HGDIOBJ bitmapMaskDummyObject;
// The actual mask
HBITMAP bitmapMaskHandle;
// 1. Generate the mask.
GetObject(bitmapHandle, sizeof(BITMAP), &bitmap);
bitmapMaskHandle = CreateBitmap(bitmap.bmWidth, bitmap.bmHeight, 1, 1, NULL);
// 2. Setup the device context for the mask (and the bitmap)
// — also get the initial selected objects in the device contexts.
bitmapDummyObject = SelectObject(bitmapGraphicsDeviceContext, (HGDIOBJ) (HBITMAP) bitmapHandle);
bitmapMaskDummyObject = SelectObject(bitmapMaskGraphicsDeviceContext, (HGDIOBJ) (HBITMAP) bitmapMaskHandle);
// 3. Set the background color of the mask.
SetBkColor(bitmapGraphicsDeviceContext, transparencyColor);
// 4. Copy the bitmap to the mask and invert it so it blends with the background color.
BitBlt(bitmapMaskGraphicsDeviceContext, 0, 0, bitmap.bmWidth, bitmap.bmHeight, bitmapGraphicsDeviceContext, 0, 0, SRCCOPY);
BitBlt(bitmapGraphicsDeviceContext, 0, 0, bitmap.bmWidth, bitmap.bmHeight, bitmapMaskGraphicsDeviceContext, 0, 0, SRCINVERT);
// 5. Select the bitmaps out before deleting the device contexts to avoid any issues.
SelectObject(bitmapGraphicsDeviceContext, bitmapDummyObject);
SelectObject(bitmapMaskGraphicsDeviceContext, bitmapMaskDummyObject);
// Clean-up
DeleteDC(bitmapGraphicsDeviceContext);
DeleteDC(bitmapMaskGraphicsDeviceContext);
// Voila!
return bitmapMaskHandle;
}
它将创建位图句柄(HBITMAP
),并且不会产生任何错误(来自GetLastError
函数)。
问题:它不会生成我应用于它的位图的单色版本,
相反,它只会创建一个仅填充黑色的位图。
那么代码是怎么回事,我在做什么错呢?
或者如何正确创建位图蒙版?
(如果可能,我会尝试在没有GDI +或其他库的情况下执行此操作)
以下是透明颜色为红色(RGB(255, 0, 0)
)的图像:
这是图像遮罩(分别是预期结果和实际结果(从左到右)):
此处参考: theForger’s Win32 API Programming Tutorial - Transparent Bitmaps
答案 0 :(得分:3)
此代码有效,尽管它并没有完全按照您认为的去做。如果您没有看到任何输出,则说明此功能的外部原因是什么。
此代码的作用是设置两个位图,以供旧的Win32技术绘制一个精灵,在该技巧中,您使用不同的光栅操作代码对BitBlt进行了两次调用,一个绘制了一个蒙版,一个绘制了一个精灵,从而精灵的背景将不会被绘制。请注意,这是创建遮罩和更改源位图。 (“ const HBITMAP bitmapHandle”中的“ const”实际上并没有做任何事情。位图句柄就像资源ID一样,指的是Windows所管理的位图,而C ++对此一无所知。制作一个const并不意味着该位图为如果您查看代码,最终的BitBlit将变为源位图,而不是掩码。该调用的作用是使源位图中的键色变黑,这是使用rop代码和两次blit绘制精灵所必需的。
顺便说一句,这项技术是一种非常古老的实现方法,在API中引入了MaskBlt可以取代您在API中进行的操作。但更进一步,MaskBlt在这一点上已经过时了。您可能想为游戏或类似游戏的游戏绘制精灵。几乎可以肯定,您真正想要的是使用每个像素的Alpha加载PNG,并使用Alpha合成对其进行绘制。您可以使用GDI+或使用FreeImage之类的开源图形库来完成此操作。
在下面的任何情况下,都有最少的代码演示此掩码代码的实际工作。只需更改以下来源,以使“ D:\ test \ hex_badge.bmp”成为您在问题中具有六角形位图的位置的路径。
#include <windows.h>
LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam);
HBITMAP g_bmp;
HBITMAP g_bmpMask;
HBITMAP createImageMask( HBITMAP bitmapHandle, const COLORREF transparencyColor) {
// For getting information about the bitmap's height and width in this context
BITMAP bitmap;
// Create the device contexts for the bitmap and its mask
HDC bitmapGraphicsDeviceContext = CreateCompatibleDC(NULL);
HDC bitmapMaskGraphicsDeviceContext = CreateCompatibleDC(NULL);
// The actual mask
HBITMAP bitmapMaskHandle;
// 1. Generate the mask.
GetObject(bitmapHandle, sizeof(BITMAP), &bitmap);
bitmapMaskHandle = CreateBitmap(bitmap.bmWidth, bitmap.bmHeight, 1, 1, NULL);
// 2. Setup the device context for the mask (and the bitmap).
SelectObject(bitmapGraphicsDeviceContext, bitmapHandle);
SelectObject(bitmapMaskGraphicsDeviceContext, bitmapMaskHandle);
// 3. Set the background color of the mask.
SetBkColor(bitmapGraphicsDeviceContext, transparencyColor);
// 4. Copy the bitmap to the mask and invert it so it blends with the background color.
BitBlt(bitmapMaskGraphicsDeviceContext, 0, 0, bitmap.bmWidth, bitmap.bmHeight, bitmapGraphicsDeviceContext, 0, 0, SRCCOPY);
BitBlt(bitmapGraphicsDeviceContext, 0, 0, bitmap.bmWidth, bitmap.bmHeight, bitmapMaskGraphicsDeviceContext, 0, 0, SRCINVERT);
// Clean-up
DeleteDC(bitmapGraphicsDeviceContext);
DeleteDC(bitmapMaskGraphicsDeviceContext);
// Voila!
return bitmapMaskHandle;
}
int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow)
{
MSG msg = { 0 };
WNDCLASS wc = { 0 };
wc.lpfnWndProc = WndProc;
wc.hInstance = hInstance;
wc.hbrBackground = (HBRUSH)(COLOR_BACKGROUND);
wc.lpszClassName = L"minwindowsapp";
g_bmp = (HBITMAP)LoadImage(hInstance, L"D:\\test\\hex_badge.bmp", IMAGE_BITMAP, 0, 0, LR_LOADFROMFILE);
g_bmpMask = createImageMask(g_bmp, RGB(255, 0, 0));
if (!RegisterClass(&wc))
return 1;
if (!CreateWindow(wc.lpszClassName,
L"Minimal Windows Application",
WS_OVERLAPPEDWINDOW | WS_VISIBLE,
0, 0, 640, 480, 0, 0, hInstance, NULL))
return 2;
while (GetMessage(&msg, NULL, 0, 0) > 0) {
TranslateMessage(&msg);
DispatchMessage(&msg);
}
return 0;
}
LRESULT HandleWmPaint(HWND hWnd, WPARAM wParam, LPARAM lParam)
{
PAINTSTRUCT ps;
HDC hdcScr = GetDC(NULL);
HDC hdcBmp = CreateCompatibleDC(hdcScr);
HBITMAP hbmOld = (HBITMAP)SelectObject(hdcBmp, g_bmp);
HDC hdcMask = CreateCompatibleDC(hdcScr);
HBITMAP hbmOldMask = (HBITMAP) SelectObject(hdcMask, g_bmpMask );
HDC hdc = BeginPaint(hWnd, &ps);
BitBlt(hdc, 0, 0, 184, 184, hdcMask, 0, 0, SRCCOPY);
BitBlt(hdc, 184, 0, 184, 184, hdcBmp, 0, 0, SRCCOPY);
EndPaint(hWnd, &ps);
SelectObject(hdcMask, hbmOldMask);
DeleteDC(hdcMask);
SelectObject(hdcBmp, hbmOld);
DeleteDC(hdcBmp);
ReleaseDC(NULL, hdcScr);
return 0;
}
LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
switch (message)
{
case WM_CLOSE:
PostQuitMessage(0);
break;
case WM_PAINT:
return HandleWmPaint(hWnd, wParam, lParam);
default:
return DefWindowProc(hWnd, message, wParam, lParam);
}
return 0;
输出如下:
我不确定为什么您确实没有得到输出,但是很可能您没有成功加载位图或者您没有成功绘制到屏幕上。