GetDIBits: trying to modify the bitmap, but not sure how to go about it? I tried lpvBits but it crashes out in the comparison in the "pig" area. How should I do this? thx
LPVOID lpvBits=NULL; // pointer to bitmap bits array
BITMAPINFO bi;
ZeroMemory(&bi.bmiHeader, sizeof(BITMAPINFOHEADER));
bi.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
if (!GetDIBits(dc, m_bmp, 0, 400, lpvBits, &bi, DIB_RGB_COLORS))
AfxMessageBox("1");
char *pig = (char*)lpvBits;
for (int m=0;m<100;m++)
{
if (pig[m] > 100)
{
pig[m] = 250;
}
}
SetDIBits( dc, m_bmp, 0, 400, (void *)pig, &bi, DIB_RGB_COLORS );
http://msdn.microsoft.com/en-us/library/dd144879(v=vs.85).aspx
lpvBits [out]
A pointer to a buffer to receive the bitmap data. If this parameter is NULL, the function passes the dimensions and format of the bitmap to the BITMAPINFO structure pointed to by the lpbi parameter.
example found here:
http://msdn.microsoft.com/en-us/library/dd183402(v=vs.85).aspx
http://msdn.microsoft.com/en-us/library/ms969901.aspx
http://www.codeproject.com/KB/graphics/drawing2bitmap.aspx
http://www.cplusplus.com/forum/general/28469/
Read the documentation for GetDIBits carefully - the lpvBits pointer is not returned to you - you need to allocate enough memory for the bitmap data you want to fetch, and pass it to GetDIBits to fill it in with image data.
Related
I have text file with the name By_a_waterfal.txt and the following content:
By a waterfal I'm calling you.
We can share it all beneath a ceiling of blue.
We'll spend a heavenly day
Here where the whispering waters play.
I create memory mapping of this file by calls of function:
HANDLE hFileMapping = CreateFileMapping(handleOfFile, NULL, PAGE_READ, 0, 0, NULL);
Where handleOfFile is the handle of By_a_waterfal.txt file.
Then I do the following call:
LPVOID lpFileMap = MapViewOfFile(hFileMapping, FILE_MAP_READ, 0, 0, 0);
How can I get access to content of the memory mapped By_a_waterfal.txt file via the view created with MapViewOfFile call?
If you really have to use memory mapping instead if std::ifstream, then:
1) Check lpFileMap for NULL.
2) Get size of view as GetFileSize(handleOfFile) or VirtualQuery(lpFileMap).
3) If file has ANSI encoding (not Unicode) cast lpFileMap to char* and proceed (do not forget that there is no 0-terminator)
auto data = static_cast<const char*>(lpFileMap);
std::string strData(data, size);
std::cout << stdData;
lpFileMap is a pointer to the content. If you want the content as a const char* for instance, just cast it:
const char* content = static_cast<const char*>(lpFileMap);
In my MFC project, I need to read and convert a Monochrome bitmap file into CByteArray. While reading the bitmap file by using 'CFile' class with the mode of 'Read', it seems like it gives more length than its original.
My MFC code:-
CFile ImgFile;
CFileException FileExcep;
CByteArray* pBinaryImage = NULL;
strFilePath.Format("%s", "D:\\Test\\Graphics0.bmp");
if(!ImgFile.Open((LPCTSTR)strFilePath,CFile::modeReadWrite,&FileExcep))
{
return NULL;
}
pBinaryImage = new CByteArray();
pBinaryImage->SetSize(ImgFile.GetLength());
// get the byte array's underlying buffer pointer
LPVOID lpvDest = pBinaryImage->GetData();
// perform a massive copy from the file to byte array
if(lpvDest)
{
ImgFile.Read(lpvDest,pBinaryImage->GetSize());
}
ImgFile.Close();
Note: File length is been set to bytearray obj.
I checked with C# with the following sample:-
Bitmap bmpImage = (Bitmap)Bitmap.FromFile("D:\\Test\\Graphics0.bmp");
ImageConverter ic = new ImageConverter();
byte[] ImgByteArray = (byte[])ic.ConvertTo(bmpImage, typeof(byte[]));
While comparing the size of "pBinaryImage" and "ImgByteArray", its not same and I guess "ImgByteArray" size is the correct one since from this array value, I can get my original bitmap back.
As I noted in comments, by reading the whole file with CFile, you are also reading the bitmap headers, which will be corrupting your data.
Here is an example function, showing how to load a monochrome bitmap from file, wrap it in MFC's CBitmap object, query the dimensions etc. and read the pixel data into an array:
void LoadMonoBmp(LPCTSTR szFilename)
{
// load bitmap from file
HBITMAP hBmp = (HBITMAP)LoadImage(NULL, szFilename, IMAGE_BITMAP, 0, 0,
LR_LOADFROMFILE | LR_MONOCHROME);
// wrap in a CBitmap for convenience
CBitmap *pBmp = CBitmap::FromHandle(hBmp);
// get dimensions etc.
BITMAP pBitMap;
pBmp->GetBitmap(&pBitMap);
// allocate a buffer for the pixel data
unsigned int uBufferSize = pBitMap.bmWidthBytes * pBitMap.bmHeight;
unsigned char *pPixels = new unsigned char[uBufferSize];
// load the pixel data
pBmp->GetBitmapBits(uBufferSize, pPixels);
// ... do something with the data ....
// release pixel data
delete [] pPixels;
pPixels = NULL;
// free the bmp
DeleteObject(hBmp);
}
The BITMAP structure will give you information about the bitmap (MSDN here) and, for a monochrome bitmap, the bits will be packed into the bytes you read. This may be another difference with the C# code, where it is possible that each bit is unpacked into a whole byte. In the MFC version, you will need to interpret this data correctly.
I am using Qt and I am new to Qt. I am getting stream of string data from server in particular port.
I am receiving 1 and 0. each time I receive one line like this
1111110001111111111111111111100000000000011111111111
After getting n number of times I need to create binary image file from the data. 1 for white and 0 for black.
How to do this? I already implement the receiving data but I have no idea how to convert this data to image.
Please help me to find the solution for this problem.
You must know dimensions of your image (for example NxM)
According to dimensions of image, you must parse string what you got (think on how to write correct cycle to get NxM 2D array from 1D array consisting NxM elements).
For holding your image data you can use QImage class. Create QImage object, passing to constructor height and width, use its method to fill image. For setting some color of pixel, you can use QImages method setPixel ( int x, int y, uint index_or_rgb ).
Thats all. Good luck!
You may try doing this way
QImage Image(500,500, QImage::Format_Indexed8);
for(int i=0;i<500/*image_width*/;i++)
{
for(int j=0;j<500/*image_height*/;j++)
{
QRgb value;
if(data[i*j] == 0)/*the data array should contain all the information*/
{
value = qRgb(0,0,0);
Image.setPixel(i,j,qGray(value))
}
else
{
value = qRgb(255,255,255);
Image.setPixel(i,j,qGray(value))
}
}
}
From Qt docs:
"Because QImage is a QPaintDevice subclass, QPainter can be used to draw directly onto images."
So, you can create QImage sized to 500x500
QImage image = QImage(500,500)
and then draw on this image
QPainter p(&image);
p.drawPoint(0,0);
p.drawPoint(0,1);
etc;
Another way is to save your bit stream into array char[] and simply create QImage with format Format_Mono or Format_MonoLSB.
QImage image = QImage(bitData, 500, 500, Format_Mono);
Thanks For help i created image. here My Code
QImage testClass::GetImage(QString rdata, int iw, int ih)
{
QImage *Image=new QImage(iw,ih,QImage::Format_ARGB32);
for(int i=0;i<ih;i++)
{
for(int j=0;j<iw;j++)
{
if(rdata.at((i*iw)+j) == '0')
Image->setPixel(QPoint(j,i),qRgb(0,0,0));
else
Image->setPixel(QPoint(j,i),qRgb(255,255,255));
}
}
return *Image;
}
I need to implement a function that receives a string containing the bytes of an image (received via boost socket connection) and converts the info into an OpenCV cv::Mat.
I also know the width and height of the image and its size in bytes. My function looks like this:
void createImageFromBytes(const std::string& name, std::pair<int,int> dimensions, const std::string& data)
{
int width,height;
width = dimensions.first;
height = dimensions.second;
//convert data to cv::Mat image
std::string filepng = DATA_PATH"/" + name +".png";
imwrite(filepng, image);
}
Which is the best method for doing this? Does OpenCV has a constructor for Mat from a string?
OpenCV Mat has a constructor from vector<byte>, but this is not so intuitive. You need to convert from string to vector this way first:
std::vector<byte> vectordata(data.begin(),data.end());
Then you can create a cv::Mat from the vector:
cv::Mat data_mat(vectordata,true);
You also need to decode the image (check documentation for which types are allowed, png, jpg, depending on the OpenCV version)
cv::Mat image(cv::imdecode(data_mat,1)); //put 0 if you want greyscale
Now you can check if the resulting size of the image is the same as the one you sent:
cout<<"Height: " << image.rows <<" Width: "<<image.cols<<endl;
Easy to trip here as the image may have null characters and any c function handling string will see null as string end
Read the image
cv::Mat image;
image = cv::imread("../test/image.png", CV_LOAD_IMAGE_COLOR);
Convert to Bytes (this is just working code, not checked for leaks)
int dataSize = image.total() * image.elemSize();
//convert to bytes
std::vector<char> vec(dataSize);
memcpy(&vec[0], reinterpret_cast<char *>(image.data), dataSize);
std::string test2(vec.begin(), vec.end());
Test and see if conversion works
//test
cv::Mat data_mat(height,width,CV_8UC3,const_cast<char*>(test2.c_str()));
imwrite("out2.png", data_mat);
If the data in the string is raw pixels (rather than a Jpeg/png etc) you can create the cv::mat directly
// assuming an RGB image in bytes
cv::Mat mat(height,width,CV_8UC3,string.data());
Here is my improved solution of Jav_Rock, the problem is that is not clear to use vector (byte type is not defined in c++, i didn't found that), instead of that, use vector, here is a example code
int func(char * pfile){
string strfile = pfile;
std::vector<unsigned char> vectordata(strfile.begin(),strfile.end());
Mat data_mat(vectordata, true);
Mat graySacleFrame = imdecode(data_mat, 0); //PGM image
...
}
EDIT: I tried using the push/pop thing, but now it crashes.
I have a feeling what I'm attempting to do is way off.. Is there any way to just get core graphics showing up on the screen? I need something thats able to be updated every frame, like drawing a line between two points that always move around..
Even if someone knows of a complete alternative Ill try it.
in .h
CGContextRef context;
in .m
in init method
int width = 100;
int height = 100;
void *buffer = calloc(1, width * height * 4);
context = CreateBitmapContextWithData(width, height, buffer);
CGContextSetRGBFillColor(context, 1, 1, 1, 1);
CGContextAddRect(context, CGRectMake(0, 0, width, height));
CGContextFillPath(context);
CGImageRef image = CGBitmapContextCreateImage(context);
hud_sprite = [CCSprite spriteWithCGImage:image key:#"hud_image1"];
free(buffer);
free(image);
hud_sprite.anchorPoint = CGPointMake(0, 0);
hud_sprite.position = CGPointMake(0, 0);
[self addChild:hud_sprite z:100];
in a method I call when I want to update it.
int width = 100;
int height = 100;
UIGraphicsPushContext(context);
CGContextClearRect(context, CGRectMake(0, 0, width, height)); //<-- crashes here. bad access...
CGContextSetRGBFillColor(context, random_float(0, 1),random_float(0, 1),random_float(0, 1), .8);
CGContextAddRect(context, CGRectMake(0, 0, width, height));
CGContextFillPath(context);
CGImageRef image = CGBitmapContextCreateImage(context);
UIGraphicsPopContext();
//CGContextRelease(ctx);
[[CCTextureCache sharedTextureCache] removeTextureForKey:#"hud_image1"];
[hud_sprite setTexture:[[CCTextureCache sharedTextureCache] addCGImage:image forKey:#"hud_image1"]];
free(image);
You are calling UIGraphicsPushContext(context). You must balance this with UIGraphicsPopContext(). Since you're not calling UIGraphicsPopContext(), you are leaving context on UIKit's graphics context stack, so it never gets deallocated.
Also, you are calling UIGraphicsBeginImageContext, which creates a new graphics context that you later release (correctly) by calling UIGraphicsEndImageContext. But you never use this context. You would access the context by calling UIGraphicsGetCurrentContext, but you never call that.
UPDATE
Never call free on a Core Foundation object!
You are getting a CGImage (which is a Core Foundation object) with this statement:
CGImageRef image = CGBitmapContextCreateImage(context);
Then later you are calling free on it:
free(image);
You must never do that.
Go read the Memory Management Programming Guide for Core Foundation. When you are done with a Core Foundation object, and you have ownership of it (because you got it from a Create function or a Copy function), you must release it with a Release function. In this case you can use either CFRelease or CGImageRelease:
CGImageRelease(image);
Furthermore, you are allocating buffer using calloc, then passing it to CreateBitmapContextWithData (which I guess is your wrapper for CGBitmapContextCreateWithData), and then freeing buffer. But context keeps a pointer to the buffer. So after you free(buffer), context has a dangling pointer. That's why you're crashing. You cannot free buffer until after you have released context.
The best way to handle this is to let CGBitmapContextCreateWithData take care of allocating the buffer itself by passing NULL as the first (data) argument. There is no reason to allocate the buffer yourself in this case.