C ++使用GetDIBits()读取像素 [英] c++ read pixels with GetDIBits()
问题描述
我试图创建一个与Windows API GetPixel()函数等效的函数,但是我想创建屏幕的位图,然后读取该缓冲区.
I'm trying to create a function which is equivalent to the windows API GetPixel() function, but I want to create a bitmap of my screen and then read that buffer.
这就是我所拥有的(大多数副本是从Google搜索中粘贴过来的),当我运行它时,它只会打印出0.我想我大部分都正确,而且我的问题是我不知道如何读取BYTE变量.
This is what I've got (Mostly copy pasted from google searches), when I run it it only prints out 0's. I think I've got most of it right, and that my issue is that I don't know how to read the BYTE variable.
所以我的问题是,我该怎么做才能使其for循环打印出一些随机的颜色(R,G或B)?
So my question is, what do I need to do in order to get it to print out some random colors (R,G or B) with my for loop?
#include <Windows.h>
#include <iostream>
#include <math.h>
#include <stdio.h>
using namespace std;
int main() {
HDC hdc,hdcMem;
hdc = GetDC(NULL);
hdcMem = CreateCompatibleDC(hdc);
HBITMAP hBitmap = CreateCompatibleBitmap(hdc, 1680, 1050);
BITMAPINFO MyBMInfo = {0};
MyBMInfo.bmiHeader.biSize = sizeof(MyBMInfo.bmiHeader);
// Get the BITMAPINFO structure from the bitmap
if(0 == GetDIBits(hdcMem, hBitmap, 0, 0, NULL, &MyBMInfo, DIB_RGB_COLORS)) {
cout << "error" << endl;
}
// create the bitmap buffer
BYTE* lpPixels = new BYTE[MyBMInfo.bmiHeader.biSizeImage];
MyBMInfo.bmiHeader.biSize = sizeof(MyBMInfo.bmiHeader);
MyBMInfo.bmiHeader.biBitCount = 32;
MyBMInfo.bmiHeader.biCompression = BI_RGB;
MyBMInfo.bmiHeader.biHeight = abs(MyBMInfo.bmiHeader.biHeight);
// get the actual bitmap buffer
if(0 == GetDIBits(hdc, hBitmap, 0, MyBMInfo.bmiHeader.biHeight, (LPVOID)lpPixels, &MyBMInfo, DIB_RGB_COLORS)) {
cout << "error2" << endl;
}
for(int i = 0; i < 100; i++) {
cout << (int)lpPixels[i] << endl;
}
return 0;
}
- Windows 7
- C :: B 13.12(控制台应用程序)
- 编译器:mingw32-gcc
- 已链接库gdi32
- Windows 7
- C::B 13.12 (Console Application)
- Compiler: mingw32-gcc
- Library gdi32 linked
推荐答案
按照约定,我将使用工作代码段添加一个新答案(我添加了缺少的lpPixels清理).请参阅我之前的答案中的讨论以及@enhzflep所做的讨论.
As agreed, I'm adding a new answer with the working code snippet (I added the missing cleanup of lpPixels). See the discussions in my previous answer and the one made by @enhzflep.
#include <Windows.h>
#include <iostream>
#include <math.h>
#include <stdio.h>
using namespace std;
HBITMAP GetScreenBmp( HDC hdc) {
// Get screen dimensions
int nScreenWidth = GetSystemMetrics(SM_CXSCREEN);
int nScreenHeight = GetSystemMetrics(SM_CYSCREEN);
// Create compatible DC, create a compatible bitmap and copy the screen using BitBlt()
HDC hCaptureDC = CreateCompatibleDC(hdc);
HBITMAP hBitmap = CreateCompatibleBitmap(hdc, nScreenWidth, nScreenHeight);
HGDIOBJ hOld = SelectObject(hCaptureDC, hBitmap);
BOOL bOK = BitBlt(hCaptureDC,0,0,nScreenWidth, nScreenHeight, hdc,0,0,SRCCOPY|CAPTUREBLT);
SelectObject(hCaptureDC, hOld); // always select the previously selected object once done
DeleteDC(hCaptureDC);
return hBitmap;
}
int main() {
HDC hdc = GetDC(0);
HBITMAP hBitmap = GetScreenBmp(hdc);
BITMAPINFO MyBMInfo = {0};
MyBMInfo.bmiHeader.biSize = sizeof(MyBMInfo.bmiHeader);
// Get the BITMAPINFO structure from the bitmap
if(0 == GetDIBits(hdc, hBitmap, 0, 0, NULL, &MyBMInfo, DIB_RGB_COLORS)) {
cout << "error" << endl;
}
// create the bitmap buffer
BYTE* lpPixels = new BYTE[MyBMInfo.bmiHeader.biSizeImage];
// Better do this here - the original bitmap might have BI_BITFILEDS, which makes it
// necessary to read the color table - you might not want this.
MyBMInfo.bmiHeader.biCompression = BI_RGB;
// get the actual bitmap buffer
if(0 == GetDIBits(hdc, hBitmap, 0, MyBMInfo.bmiHeader.biHeight, (LPVOID)lpPixels, &MyBMInfo, DIB_RGB_COLORS)) {
cout << "error2" << endl;
}
for(int i = 0; i < 100; i++) {
cout << (int)lpPixels[i];
}
DeleteObject(hBitmap);
ReleaseDC(NULL, hdc);
delete[] lpPixels;
return 0;
}
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