I am trying to get a uint8_t[] of a portion of the screen. The xy coordinates of the top left is 2,3 and of bottom right is 17,18.
This is the top 30x30 pixels of my screen with regular screenshot and photoshop crop:
And this is what 2,3 to 17,18 screenshot should look like via regular screenshot and Photoshop crop:
This is what I am getting as a result of my code:
My code is in js-ctypes but there is no ctypes errors. This is a winapi thing. So I didn't tag this with ctypes as they would be confused. This is the simplified code I am using, the error checks etc have been removed:
c1 = {x:2, y:3} // top left corner
c2 = {x:17, y:18} // bottom right corner
CreateDC('DISPLAY', null, null, null);
nBPP = GetDeviceCaps(hdcScreen, BITSPIXEL);
w = c2.x - c1.x; // width = 15
h = c2.y - c1.y; // height = 15
hdcMemoryDC = CreateCompatibleDC(hdcScreen);
bmi = BITMAPINFO();
bmi.bmiHeader.biSize = BITMAPINFOHEADER.size;
bmi.bmiHeader.biWidth = w;
bmi.bmiHeader.biHeight = -1 * h;
bmiHeader.biPlanes = 1;
bmi.bmiHeader.biBitCount = nBPP; // nBPP is 32
bmi.bmiHeader.biCompression = BI_RGB;
hbmp = CreateDIBSection(hdcScreen, &bmi, DIB_RGB_COLORS, (void**)&pixelBuffer, null, 0);
SelectObject(hdcMemoryDC, hbmp);
BitBlt(hdcMemoryDC, 0, 0, w, h, hdcScreen, c1.x, c1.y, SRCCOPY);
Why portion of screen bits come out wrong? If I do a full screen shot it works fine.
Related
I am writing a win32 low level gui app that emulates a console app. I use a fixed width font, my test uses Cascadia Mono, but I have the same issue with any fixed width font.
The console app is trying to draw a horizontal line using U2500 character.
I output the characters that app is passing me one by one. When I do that I get spaces between the horizontal lines, when I output in one call to textout those gaps are filled in.
I made this using the VS c++ windows app template and added this code to the WM_PAINT handling
auto nHeight = -MulDiv(48, GetDeviceCaps(hdc, LOGPIXELSY), 72);
auto hfont = CreateFont(
nHeight,
0,
0,
0,
100,//200,
0,
0,
0,
DEFAULT_CHARSET,
OUT_OUTLINE_PRECIS,
CLIP_DEFAULT_PRECIS,
CLEARTYPE_QUALITY,
FIXED_PITCH,
L"Cascadia Mono"
);
TEXTMETRIC tm;
SelectObject(hdc, hfont);
GetTextMetrics(hdc, &tm);
auto str = L"kkkkkk─────k";
TextOut(hdc, 0, 0, L"kkkkkk─────k", 12);
for (int i = 0; i < 12; i++)
{
TextOut(hdc, i * tm.tmAveCharWidth, tm.tmHeight, &str[i], 1);
}
This displays
you can see that this is not due to me miscalculating the char cell width, the strings are exactly aligned , just there are some added pixels in the upper one, also notice some extra 'knobiness' where the joins are. V odd. Also note that the right edge of the last K before the line starts is slightly chopped off in the char by char one, but not in the all at once one.
So why am I doing it char by char, because I need to specify font weight, bg, fg for each cell.
Instead of using TextOut, you can use DrawText which is a bit more hi-level, like this:
for (int i = 0; i < 12; i++)
{
RECT rc;
rc.left = i * tm.tmAveCharWidth;
rc.top = tm.tmHeight;
rc.right = rc.left + 50; // todo: make sure this is ok
rc.bottom = rc.top + 100;
DrawText(hdc, (LPWSTR)&str[i], 1, &rc, 0);
}
And it seems to fix the "lineness" of it, although it's not 100% exactly the same (there are some pixels that show a difference):
I have tried this code. 540 is the left most x value of the box,3 is left most y value of the box,262 - width ,23 -height of the region which I am going to calculate the ratio of the white/black pixels. What I really wanted to do is detect the number of white/black pixel ratio in a specific region.I have calculate the coordinates for each cell (regions which I am going to specified)and try with this code.But the error in counting.
Can I please have an idea about this issue please..
I am really stuck here with my final year project.
CvSize cvSize = cvSize(img.width(), img.height());
IplImage image = cvCreateImage(cvSize, IPL_DEPTH_8U, 1);
IplImage image2 = cvCreateImage(cvSize, IPL_DEPTH_8U, 3);
cvCvtColor(image2, image, CV_RGB2GRAY);
cvSetImageROI(image2, cvRect(540,3,262,23));
//IplImage image2 = cvCreateImage(cvSize, IPL_DEPTH_8U, 3);
//
//cvCvtColor(arg0, arg1, arg2)
// cvCvtColor(image2, image, CV_RGB2GRAY);
//cvThreshold(image, image, 128, 255, CV_THRESH_BINARY);
CvLineIterator iterator = new CvLineIterator();
double sum = 0, green_sum = 0, red_sum = 0;
CvPoint p2 = new CvPoint(802,3);
CvPoint p1 = new CvPoint(540,26);
int lineCount = cvInitLineIterator(image2, p1, p2, iterator, 8, 0 );
for (int i = 0; i < lineCount; i++) {
sum += iterator.ptr().get() & 0xFF;
}
System.out.println("sum................"+sum);
CV_NEXT_LINE_POINT(iterator);
}
}
it gave the result as sum................0.0
I have really stuck with this..can you please give any solution for this issue please
Move CV_NEXT_LINE_POINT(iterator); line inside the for loop. Then it should work.
I need to import a PNG and display it on screen in a Motif application. For reasons best known to myself, I don't want to use any more libraries than I need to, and I'd like to stick with just Motif and pnglib.
I've been battling with this for a couple of days now, and I'd like to put aside my pride and ask for some help. This screenshot shows the problem:
https://s3.amazonaws.com/gtrebol264929/pnglib_fail.png
The window on the right shows what the image should look like, the window on the left is my Motif application showing what it looks like in my app. Clearly I've got the image data OK, as the basic concept of the picture can be seen. But also clearly I've messed up how I get the pixel data from pnglib into an XImage. Below is my code:
char * xdata = malloc(width * height * (channels + 1));
memset(xdata,100,width * height * channels);
int colc = 0;
int bytec = 0;
while (colc < width) {
int rowc = 0;
while(rowc < height) {
png_byte * row = png.row_pointers[rowc];
memcpy(&xdata[bytec],&row[colc],1);
bytec += 4;
rowc += 1;
}
colc += 1;
}
XImage * img = XCreateImage(display, CopyFromParent, depth * channels, ZPixmap, 0, xdata, width, height, 32, bytes_per_line);
printf("PNG %ix%i (depth: %i x %i) img: %p\n",width,height,depth,channels,img);
XPutImage (display, win, gc, img, 0, 0, 0, 0, width, height); // 0, 0, 0, 0 are src x,y and dst x,y
png.row_pointers is the pixel data from pnglib.
I'm pretty sure I've just misunderstood how the pixel data is stored, but I can't quite work out what I've done wrong. Any help is very much appreciated.
All the best
Garry
The below code helps me to convert OpenGL output to JPEG image using libjpg but the resultant image is flipped vertical...
The code works perfect but the final image is flipped I dont know why ?!
unsigned char *pdata = new unsigned char[width*height*3];
glReadPixels(0, 0, width, height, GL_RGB, GL_UNSIGNED_BYTE, pdata);
FILE *outfile;
if ((outfile = fopen("sample.jpeg", "wb")) == NULL) {
printf("can't open %s");
exit(1);
}
struct jpeg_compress_struct cinfo;
struct jpeg_error_mgr jerr;
cinfo.err = jpeg_std_error(&jerr);
jpeg_create_compress(&cinfo);
jpeg_stdio_dest(&cinfo, outfile);
cinfo.image_width = width;
cinfo.image_height = height;
cinfo.input_components = 3;
cinfo.in_color_space = JCS_RGB;
jpeg_set_defaults(&cinfo);
/*set the quality [0..100] */
jpeg_set_quality (&cinfo, 100, true);
jpeg_start_compress(&cinfo, true);
JSAMPROW row_pointer;
int row_stride = width * 3;
while (cinfo.next_scanline < cinfo.image_height) {
row_pointer = (JSAMPROW) &pdata[cinfo.next_scanline*row_stride];
jpeg_write_scanlines(&cinfo, &row_pointer, 1);
}
jpeg_finish_compress(&cinfo);
fclose(outfile);
jpeg_destroy_compress(&cinfo);
OpenGL's coordinate system has the origin in the lower left corner of the image. LIBJPEG assumes that the origin of the image is in the upper left corner of the image. Make the following change to fix your code:
while (cinfo.next_scanline < cinfo.image_height)
{
row_pointer = (JSAMPROW) &pdata[(cinfo.image_height-1-cinfo.next_scanline)*row_stride];
jpeg_write_scanlines(&cinfo, &row_pointer, 1);
}
I'm using UpdateLayeredWindow to display an application window. I have created my own custom buttons and i would like to create my own static text. The problem is that when i try to draw the text on the hdc, the DrawText or TextOut functions overwrite the alpha channel of my picture and the text will become transparent. I tried to find a solution to this but i could not find any. My custom controls are designed in such way that they will do all the drawing in a member function called Draw(HDC hDc), so they can only access the hdc. I would like to keep this design. Can anyone help me? I am using MFC and i would want to achieve the desired result without the use of GDI+.
I know this is an old post ... but I just had this very same problem ... and it was driving me CRAZY.
Eventually, I stumbled upon this post by Mike Sutton to the microsoft.public.win32.programmer.gdi newsgroup ... from almost 7 years ago!
Basically, the DrawText (and TextOut) do not play nicely with the alpha channel and UpdateLayeredWindow ... and you need to premultiply the R, G, and B channels with the alpha channel.
In Mike's post, he shows how he creates another DIB (device independent bitmap) upon which he draws the text ... and alpha blends that into the other bitmap.
After doing this, my text looked perfect!
Just in case, the link to the newsgroup post dies ... I am going to include the code here. All credit goes to Mike Sutton (#mikedsutton).
Here is the code that creates the alpha blended bitmap with the text on it:
HBITMAP CreateAlphaTextBitmap(LPCSTR inText, HFONT inFont, COLORREF inColour)
{
int TextLength = (int)strlen(inText);
if (TextLength <= 0) return NULL;
// Create DC and select font into it
HDC hTextDC = CreateCompatibleDC(NULL);
HFONT hOldFont = (HFONT)SelectObject(hTextDC, inFont);
HBITMAP hMyDIB = NULL;
// Get text area
RECT TextArea = {0, 0, 0, 0};
DrawText(hTextDC, inText, TextLength, &TextArea, DT_CALCRECT);
if ((TextArea.right > TextArea.left) && (TextArea.bottom > TextArea.top))
{
BITMAPINFOHEADER BMIH;
memset(&BMIH, 0x0, sizeof(BITMAPINFOHEADER));
void *pvBits = NULL;
// Specify DIB setup
BMIH.biSize = sizeof(BMIH);
BMIH.biWidth = TextArea.right - TextArea.left;
BMIH.biHeight = TextArea.bottom - TextArea.top;
BMIH.biPlanes = 1;
BMIH.biBitCount = 32;
BMIH.biCompression = BI_RGB;
// Create and select DIB into DC
hMyDIB = CreateDIBSection(hTextDC, (LPBITMAPINFO)&BMIH, 0, (LPVOID*)&pvBits, NULL, 0);
HBITMAP hOldBMP = (HBITMAP)SelectObject(hTextDC, hMyDIB);
if (hOldBMP != NULL)
{
// Set up DC properties
SetTextColor(hTextDC, 0x00FFFFFF);
SetBkColor(hTextDC, 0x00000000);
SetBkMode(hTextDC, OPAQUE);
// Draw text to buffer
DrawText(hTextDC, inText, TextLength, &TextArea, DT_NOCLIP);
BYTE* DataPtr = (BYTE*)pvBits;
BYTE FillR = GetRValue(inColour);
BYTE FillG = GetGValue(inColour);
BYTE FillB = GetBValue(inColour);
BYTE ThisA;
for (int LoopY = 0; LoopY < BMIH.biHeight; LoopY++) {
for (int LoopX = 0; LoopX < BMIH.biWidth; LoopX++) {
ThisA = *DataPtr; // Move alpha and pre-multiply with RGB
*DataPtr++ = (FillB * ThisA) >> 8;
*DataPtr++ = (FillG * ThisA) >> 8;
*DataPtr++ = (FillR * ThisA) >> 8;
*DataPtr++ = ThisA; // Set Alpha
}
}
// De-select bitmap
SelectObject(hTextDC, hOldBMP);
}
}
// De-select font and destroy temp DC
SelectObject(hTextDC, hOldFont);
DeleteDC(hTextDC);
// Return DIBSection
return hMyDIB;
}
Here is the code that drives the CreateAlphaTextBitmap method:
void TestAlphaText(HDC inDC, int inX, int inY)
{
const char *DemoText = "Hello World!\0";
RECT TextArea = {0, 0, 0, 0};
HFONT TempFont = CreateFont(50, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, "Arial\0");
HBITMAP MyBMP = CreateAlphaTextBitmap(DemoText, TempFont, 0xFF);
DeleteObject(TempFont);
if (MyBMP)
{
// Create temporary DC and select new Bitmap into it
HDC hTempDC = CreateCompatibleDC(inDC);
HBITMAP hOldBMP = (HBITMAP)SelectObject(hTempDC, MyBMP);
if (hOldBMP)
{
// Get Bitmap image size
BITMAP BMInf;
GetObject(MyBMP, sizeof(BITMAP), &BMInf);
// Fill blend function and blend new text to window
BLENDFUNCTION bf;
bf.BlendOp = AC_SRC_OVER;
bf.BlendFlags = 0;
bf.SourceConstantAlpha = 0x80;
bf.AlphaFormat = AC_SRC_ALPHA;
AlphaBlend(inDC, inX, inY, BMInf.bmWidth, BMInf.bmHeight, hTempDC, 0, 0, BMInf.bmWidth, BMInf.bmHeight, bf);
// Clean up
SelectObject(hTempDC, hOldBMP);
DeleteObject(MyBMP);
DeleteDC(hTempDC);
}
}
}