I have an image in memory with the following byte layout
blue, green, red, alpha (32 bits per pixel)
The alpha is not used.
I want to draw it to a window using GDI. Later I may want to draw only a smaller part of it to the window. But the bitmap in memory is always fixed at a certain width & height.
How can this bitmap drawing operation be done?
SetDIBitsToDevice and/or StretchDIBits can be used to draw pixel data directly to a HDC if the pixel data is in a format that can be specified in a BITMAPINFOHEADER. If your color values are not in the correct order you must set the compression to BI_BITFIELDS instead of BI_RGB and append 3 DWORDs as the color mask after BITMAPINFOHEADER in memory.
case WM_PAINT:
{
RECT rc;
GetClientRect(hWnd, &rc);
PAINTSTRUCT ps;
HDC hDC = wParam ? (HDC) wParam : BeginPaint(hWnd, &ps);
static const UINT32 pixeldata[] = { ARGB(255,255,0,0), ARGB(255,255,0,255), ARGB(255,255,255,0), ARGB(255,0,0,0) };
BYTE bitmapinfo[FIELD_OFFSET(BITMAPINFO,bmiColors) + (3 * sizeof(DWORD))];
BITMAPINFOHEADER &bih = *(BITMAPINFOHEADER*) bitmapinfo;
bih.biSize = sizeof(BITMAPINFOHEADER);
bih.biWidth = 2, bih.biHeight = 2;
bih.biPlanes = 1, bih.biBitCount = 32;
bih.biCompression = BI_BITFIELDS, bih.biSizeImage = 0;
bih.biClrUsed = bih.biClrImportant = 0;
DWORD *pMasks = (DWORD*) (&bitmapinfo[bih.biSize]);
pMasks[0] = 0xff0000; // Red
pMasks[1] = 0x00ff00; // Green
pMasks[2] = 0x0000ff; // Blue
StretchDIBits(hDC, 0, 0, rc.right, rc.bottom, 0, 0, 2, 2, pixeldata, (BITMAPINFO*) &bih, DIB_RGB_COLORS, SRCCOPY);
return !(wParam || EndPaint(hWnd, &ps));
}
Related
I am going to create some kind of "remote desktop" application that streams the content of the screen over a socket to a connected client.
In order to take a screenshot, I've come up with the following piece of code, which is a modified version of examples I've seen here and there.
#include <windows.h>
#include <tchar.h>
#include <stdio.h>
int _tmain( int argc, _TCHAR * argv[] )
{
int ScreenX = 0;
int ScreenY = 0;
BYTE* ScreenData = 0;
HDC hScreen = GetDC(GetDesktopWindow());
ScreenX = GetDeviceCaps(hScreen, HORZRES);
ScreenY = GetDeviceCaps(hScreen, VERTRES);
ScreenData = (BYTE*)calloc(4 * ScreenX * ScreenY, sizeof(BYTE) );
BITMAPINFOHEADER bmi = {0};
bmi.biSize = sizeof(BITMAPINFOHEADER);
bmi.biPlanes = 1;
bmi.biBitCount = 32;
bmi.biWidth = ScreenX;
bmi.biHeight = -ScreenY;
bmi.biCompression = BI_RGB;
bmi.biSizeImage = 0; // 3 * ScreenX * ScreenY;
int iBegTc = ::GetTickCount();
// Take 100 screen captures for a more accurante measurement of the duration.
for( int i = 0; i < 100; ++i )
{
HBITMAP hBitmap = CreateCompatibleBitmap(hScreen, ScreenX, ScreenY);
HDC hdcMem = CreateCompatibleDC (hScreen);
HGDIOBJ hOld = SelectObject(hdcMem, hBitmap);
BitBlt(hdcMem, 0, 0, ScreenX, ScreenY, hScreen, 0, 0, SRCCOPY);
SelectObject(hdcMem, hOld);
GetDIBits(hdcMem, hBitmap, 0, ScreenY, ScreenData, (BITMAPINFO*)&bmi, DIB_RGB_COLORS);
DeleteDC(hdcMem);
DeleteObject(hBitmap);
}
int iEndTc = ::GetTickCount();
printf( "%d ms", (iEndTc - iBegTc) / 100 );
system("PAUSE");
ReleaseDC(GetDesktopWindow(),hScreen);
return 0;
}
My problem is that the code within the loop takes too long too execute. In my case it's about 36 ms per iteration.
I am wondering if there are statements that could be done just once and thus put outside of the loop, likI did for the byte buffer. I don't know however which are the ones that I must do for each new image, and which are the ones I can only do one time.
Keep BitBlt and GetDIBits inside the loop, move the rest outside the loop as follows:
HBITMAP hBitmap = CreateCompatibleBitmap(hScreen, ScreenX, ScreenY);
HDC hdcMem = CreateCompatibleDC (hScreen);
HGDIOBJ hOld = SelectObject(hdcMem, hBitmap);
for( int i = 0; i < 100; ++i )
{
BitBlt(hdcMem, 0, 0, ScreenX, ScreenY, hScreen, 0, 0, SRCCOPY);
//hBitmap is updated now
GetDIBits(hdcMem, hBitmap, 0, ScreenY, ScreenData, (BITMAPINFO*)&bmi, DIB_RGB_COLORS);
//wait...
}
SelectObject(hdcMem, hOld);
DeleteDC(hdcMem);
DeleteObject(hBitmap);
In addition bmi.biSizeImage should be set to data size, in this case 4 * ScreenX * ScreenY
This won't make the code noticeably faster. The bottle neck is at BitBlt. It's still about 30 frames/sec, this should be okay unless there is a game or movie on the screen.
You might also try saving to a 24 bit bitmap. It won't make any difference in this code but data size would be smaller ((width * bitcount + 31) / 32) * 4 * height)
The Aero feature of Windows seems to affect the BitBlt speed.
If you iteratively BitBlt even one pixel from the display, it will run at about 30 frames per second, and the CPU usage will be near idle. But if you turn off the Aero feature of Windows, you'll get BitBlt speeds that are remarkably faster.
I've been asking a lot of questions about text aliasing and line aliasing and transparency lately because I wanted to write a platform agnostic vector graphics system for Go; the Windows code is written in C. Premultiplication shenanigans have led me to change the focus over to just rendering text (so I can access system fonts).
Right now I have something that draws text to an offscreen bitmap. This works, except for the antialiased bits. In my code, as I fill the memory buffer with 0xFF to flip the alpha byte (which GDI sets to 0x00 for a pixel that is drawn), the antialiasing is to white. Other people have seen antialiasing to black. This happens with both ANTIALIASED_QUALITY and CLEARTYPE_QUALITY.
I am drawing with TextOut() into a DIB in this case. The DIB is backed by a copy of the screen DC (GetDC(NULL)).
Is there anything I can do to just get text transparent? Can I somehow detect the white pixels, unblend them, and convert that to an alpha? How would I do that for colors too similar to white?
I wrote some code to do this.
The AntialiasedText function draws anti-aliased text onto an off-screen bitmap. It calculates the transparency so that the text can be blended with any background using the AlphaBlend API function.
The function is followed by a WM_PAINT handler illustrating its use.
// Yeah, I'm lazy...
const int BitmapWidth = 500;
const int BitmapHeight = 128;
// Draw "text" using the specified font and colour and return an anti-aliased bitmap
HBITMAP AntialiasedText(LOGFONT* plf, COLORREF colour, LPCWSTR text)
{
BITMAPINFO bmi = {0};
bmi.bmiHeader.biSize = sizeof(bmi.bmiHeader);
bmi.bmiHeader.biWidth = BitmapWidth;
bmi.bmiHeader.biHeight = BitmapHeight;
bmi.bmiHeader.biPlanes = 1;
bmi.bmiHeader.biBitCount = 32;
LPBYTE pBits;
HBITMAP hDIB = CreateDIBSection(0, &bmi, DIB_RGB_COLORS, (LPVOID*)&pBits, 0, 0);
// Don't want ClearType
LOGFONT lf = *plf;
lf.lfQuality = ANTIALIASED_QUALITY;
HFONT hFont = CreateFontIndirect(&lf);
HDC hScreenDC = GetDC(0);
HDC hDC = CreateCompatibleDC(hScreenDC);
ReleaseDC(0, hScreenDC);
HBITMAP hOldBMP = (HBITMAP)SelectObject(hDC, hDIB);
HFONT hOldFont = (HFONT)SelectObject(hDC, hFont);
RECT rect = {0, 0, BitmapWidth, BitmapHeight};
FillRect(hDC, &rect, WHITE_BRUSH);
TextOut(hDC, 2, 2, text, wcslen(text));
// Flush drawing
GdiFlush();
// Calculate alpha
LPBYTE pixel = pBits;
int pixelCount = BitmapWidth * BitmapHeight;
BYTE r = GetRValue(colour);
BYTE g = GetGValue(colour);
BYTE b = GetBValue(colour);
for (int c = 0; c != pixelCount; ++c)
{
// Set alpha
BYTE alpha = 255 - pixel[0];
pixel[3] = alpha;
// Set colour
pixel[0] = b * alpha / 255;
pixel[1] = g * alpha / 255;
pixel[2] = r * alpha / 255;
pixel += 4;
}
SelectObject(hDC, hOldFont);
SelectObject(hDC, hOldBMP);
DeleteDC(hDC);
DeleteObject(hFont);
return hDIB;
}
Here's a WM_PAINT handler to exercise the function. It draws the same text twice, first using TextOut and then using the anti-aliased bitmap. They look much the same, though not as good as ClearType.
case WM_PAINT:
{
LPCWSTR someText = L"Some text";
hdc = BeginPaint(hWnd, &ps);
LOGFONT font = {0};
font.lfHeight = 40;
font.lfWeight = FW_NORMAL;
wcscpy_s(font.lfFaceName, L"Comic Sans MS");
// Draw the text directly to compare to the bitmap
font.lfQuality = ANTIALIASED_QUALITY;
HFONT hFont = CreateFontIndirect(&font);
font.lfQuality = 0;
HFONT hOldFont = (HFONT)SelectObject(hdc, hFont);
TextOut(hdc, 2, 10, someText, wcslen(someText));
SelectObject(hdc, hOldFont);
DeleteObject(hFont);
// Get an antialiased bitmap and draw it to the screen
HBITMAP hBmp = AntialiasedText(&font, RGB(0, 0, 0), someText);
HDC hScreenDC = GetDC(0);
HDC hBmpDC = CreateCompatibleDC(hScreenDC);
ReleaseDC(0, hScreenDC);
HBITMAP hOldBMP = (HBITMAP)SelectObject(hBmpDC, hBmp);
BLENDFUNCTION bf;
bf.BlendOp = AC_SRC_OVER;
bf.BlendFlags = 0;
bf.SourceConstantAlpha = 255;
bf.AlphaFormat = AC_SRC_ALPHA;
int x = 0;
int y = 40;
AlphaBlend(hdc, x, y, BitmapWidth, BitmapHeight, hBmpDC, 0, 0, BitmapWidth, BitmapHeight, bf);
SelectObject(hBmpDC, hOldBMP);
DeleteDC(hBmpDC);
DeleteObject(hBmp);
EndPaint(hWnd, &ps);
}
break;
I have a small code snippet which loads an image from a PNG file, then modifies the image data in memory by making a specific color transparent (setting alpha to 0 for that color). Here's the code itself:
static gboolean expose (GtkWidget *widget, GdkEventExpose *event, gpointer userdata)
{
int width, height, stride, x, y;
cairo_t *cr = gdk_cairo_create(widget->window);
cairo_surface_t* image;
char* ptr;
if (supports_alpha)
cairo_set_source_rgba (cr, 1.0, 1.0, 1.0, 0.0); /* transparent */
else
cairo_set_source_rgb (cr, 1.0, 1.0, 1.0); /* opaque white */
cairo_set_operator (cr, CAIRO_OPERATOR_SOURCE);
cairo_paint (cr);
image = cairo_image_surface_create_from_png ("bg.png");
width = cairo_image_surface_get_width (image);
height = cairo_image_surface_get_height (image);
stride = cairo_image_surface_get_stride (image);
cairo_surface_flush (image);
ptr = (unsigned char*)malloc (stride * height);
memcpy (ptr, cairo_image_surface_get_data (image), stride * height);
cairo_surface_destroy (image);
image = cairo_image_surface_create_for_data (ptr, CAIRO_FORMAT_ARGB32, width, height, stride);
cairo_surface_flush (image);
for (y = 0; y < height; y++) {
for (x = 0; x < width; x++) {
char alpha = 0;
unsigned int z = *((unsigned int*)&ptr [y * stride + x * 4]);
if ((z & 0xffffff) == 0xffffff) {
z = (z & ~0xff000000) | (alpha & 0xff000000);
*((unsigned int*) &ptr [y * stride + x * 4]) = z;
}
}
}
cairo_surface_mark_dirty (image);
cairo_surface_write_to_png (image, "image.png");
gtk_widget_set_size_request (GTK_OBJECT (window), width, height);
gtk_window_set_resizable (GTK_OBJECT (window), FALSE);
cairo_set_source_surface (cr, image, 0, 0);
cairo_paint_with_alpha (cr, 0.9);
cairo_destroy (cr);
cairo_surface_destroy (image);
free (ptr);
return FALSE;
}
When I dump the modified data to PNG, transparency is actually there. But when the same data is used as a source surface for painting, there's no transparency. What might be wrong?
Attachments:
image.png - modified data dumped to file for debugging purposes,
demo.png - actual result
bg.png - source image, is omitted due to stackoverflow restrictions, it's simply black rounded rectangle on the white background. Expected result is black translucent rectangle and completely transparent fields, not white, like these on the demo.png.
Setting alpha to 0 means that the color is completely transparent. Since cairo uses pre-multiplied alpha, you have to set the pixel to 0, since otherwise the color components could have higher values than the alpha channels. I think cairo chokes on those super-luminscent pixels.
So instead of this code:
if ((z & 0xffffff) == 0xffffff) {
z = (z & ~0xff000000) | (alpha & 0xff000000);
*((unsigned int*) &ptr [y * stride + x * 4]) = z;
}
You should try the following:
if ((z & 0xffffff) == 0xffffff) {
*((unsigned int*) &ptr [y * stride + x * 4]) = 0;
}
And while we are at it:
Doesn't (z & 0xffffff) == 0xffffff check if the green, blue and alpha channels are all at 100% and ignores the red channel? Are you sure that's really what you want? z == 0xffffffff would be opaque white.
Instead of using unsigned int, it would be better if you used uint32_t for accessing the pixel data. Portability!
Your code assumes that cairo_image_surface_create_from_png() always gives you an image surface with format ARGB32. I don't think that's necessarily always correct and e.g. RGB24 is possible as well.
I think I would do something like this:
for (y = 0; y < height; y++) {
uint32_t row = (uint32_t *) &ptr[y * stride];
for (x = 0; x < width; x++) {
uint32_t px = row[x];
if (is_expected_color(px))
row[x] = 0;
}
}
I'm using VisualStudio 2010, coding in C++/CLI, and doing all the graphics by GDI. I have a little app that plot continuously a Gaussian curve with some noise added. Every point is added real-time just like I pointed in this post.
Now, my task is to create a little colored area that I can shrink and increase to select a portion of the plot and do some math.
This kind of task is managed by a MouseMove event just like that:
System::Void Form1::pictureBox1_MouseMove(System::Object^ sender, System::Windows::Forms::MouseEventArgs^ e) {
//Recalculate the position of the area,
//clean up the old one and redraw a new.
}
It works actually but I'm experiencing a bit graphic "bug".
As you can see, while I'm moving the area, everything under it is been deleted. The grid is here simply because it is static and I'm refreshing it everytime the green area is redrawn.
Actually it is not a bug, for sure it must go like that. To me, it is kinda obvious. I called it like that because it is not what I'm expecting.
I'm asking if there is a way to the green area as if it is upon a different layer. In this way, I would be able to move the green area while the plot is running without being erased.
I tried handling 2 HDC variables and plot the graph and the grid on the first one and the green area on the second one, but it seems not working.
Do you have some nice idea to get through this bad ( to me ) behaviour - maybe with some multilayer thing or some other fancy solutions - or should I give up and waiting for replotting?
Thanks everyone will give me an answer! :)
EDIT:
Here is how I draw my dataseries:
for(int i = 1; i<=1000; i++ ) {
Gauss[i] = safe_cast<float>(Math::Round( a*s*Math::Exp(-Math::Pow(((0.01*1*(i))-portante), 2)/b), 2));
Rumore[i] = safe_cast<float>(Math::Round(r*generatore->NextDouble(), 2));
SelectObject(hdcPictureBox, LinePen);
MoveToEx(hdcPictureBox, i-1+50, 500-convY*(Gauss[i-1]+Rumore[i-1])+50, NULL);
LineTo(hdcPictureBox, i+50, 500-convY*(Gauss[i]+Rumore[i])+50);
e1 = (i+k)%1000; //Buffer
if(i>DXX-54 && i<SXX-54) {
//ErasePen1 = CreatePen(PS_SOLID, 1, RGB(216,191,216));
label1->Text = Convert::ToString(i);
label1->Refresh();
SelectObject(hdcPictureBox, ErasePen1);
}
else {
SelectObject(hdcPictureBox, ErasePen);
}
//HPEN ErasePen1 = CreatePen(PS_SOLID, 1, RGB(216,191,216));
MoveToEx(hdcPictureBox, e1+50, 500-convY*(Gauss[e1]+Rumore[e1])+50, NULL);
LineTo(hdcPictureBox, e1+1+50, 500-convY*(Gauss[e1+1]+Rumore[e1+1])+50);
}
where DXX and SXX are the X-coordinates of areas - DXX starting, SXX ending.
This is how I'm handling the MouseMove. Do_Chan and Do_Clean are essentially the same thing. Do_Clean draws a bigger area with the background color to erase the old area and allowing Do_Chan to draw a new one.
System::Void Form1::pictureBox1_MouseMove(System::Object^ sender, System::Windows::Forms::MouseEventArgs^ e) {
if(e->Button == System::Windows::Forms::MouseButtons::Left) {
double span100 = (SXX-DXX)*85/100;
if (e->X > DXX+((SXX-DXX)/2)-15 && e->X < DXX+((SXX-DXX)/2)+15 && (e->Y >30 && e->Y <50)
|| e->X >DXX+((SXX-DXX)/2)-span100/2 && e->X < DXX+((SXX-DXX)/2)+span100/2 && (e->Y >50 && e->Y <550)) {
HBRUSH brush = CreateSolidBrush(RGB(245,255,250));
Do_Clean(hdcPictureBox, DXX, SXX, brush);
double spawn = SXX-DXX;
DXX = e->X - spawn/2;
SXX = e->X + spawn/2;
if(DXX < 50) {
DXX = 51;
}
if(SXX >1050 ) {
SXX = 1049;
}
spawn = SXX - DXX;
CXX = DXX + spawn/2;
HBRUSH brush1 = CreateSolidBrush(RGB(166,251,178));
Do_Chan(hdcPictureBox2, DXX, SXX, brush1);
int k = 4;
int e1 = 0;
for(int i = 1; i<=1000; i++) {
SelectObject(hdcPictureBox, LinePen);
MoveToEx(hdcPictureBox, i-1+50, 500-250*(Gauss[i-1]+Rumore[i-1])+50, NULL);
LineTo(hdcPictureBox, i+50, 500-250*(Gauss[i]+Rumore[i])+50);
e1 = (i+k)%1000; //Buffer
if(i>DXX-54 && i<SXX-54) {
//ErasePen1 = CreatePen(PS_SOLID, 1, RGB(216,191,216));
SelectObject(hdcPictureBox, ErasePen1);
}
else {
SelectObject(hdcPictureBox, ErasePen);
}
//HPEN ErasePen1 = CreatePen(PS_SOLID, 1, RGB(216,191,216));
MoveToEx(hdcPictureBox, e1+50, 500-250*(Gauss[e1]+Rumore[e1])+50, NULL);
LineTo(hdcPictureBox, e1+1+50, 500-250*(Gauss[e1+1]+Rumore[e1+1])+50);
}
}
}
}
As you can see, after I drew the new area, I redraw all the point of the array Gauss+Rumore.
This is how Do_Chan ( Do_Clean is the same ) works:
void Do_Chan(HDC hdc, int dx, int sx, HBRUSH brush) {
//i = 250, y = 50
int y = 50;
int spawn = sx - dx;
HPEN pen = CreatePen(PS_SOLID, 1, RGB(245, 255, 250));
HPEN penC = CreatePen(PS_DOT, 1, RGB(0, 0, 0));
/*Fai il rettangolo */
SelectObject(hdc, pen);
SelectObject(hdc, brush);
POINT punti[4];
punti[0].x = dx;
punti[0].y = y;
punti[1].x = dx +spawn;
punti[1].y = y;
punti[2].x = dx + spawn;
punti[2].y = y+500;
punti[3].x = dx;
punti[3].y = y+500;
Polygon(hdc, punti, 4);
Ellipse(hdc, dx-10, y-20, dx+10, y);
SelectObject(hdc, penC);
MoveToEx(hdc, dx+spawn/2, 50,NULL);
LineTo(hdc, dx+spawn/2, 550);
SelectObject(hdc, pen);
SelectObject(hdc, brush);
Ellipse(hdc, dx-10+spawn/2, y-20, dx+10+spawn/2, y);
SelectObject(hdc, pen);
SelectObject(hdc, brush);
Ellipse(hdc, dx-10+spawn, y-20, dx+10+spawn, y);
//Plot the axis and the grid
}
I have thought of a possible way to do it and every solution had a drawback. For example
creating a thread. It has a drawback of drawing to picturebox dc from a different thread than the one handling the message queue. Not recomended
Another one:
using a timer and for every tick(lets say 16msec) draw. The DXX and SXX will be global variables. In picturebox move event you will only calculate these values(no drawing), also use some critical sections to protect them, and do all the drawing inside tick of timer. This works but you probable encounter some delay if your movement in picturebox is faster than 60fps.
The solution that i came finally was:
Inside your infinite loop:
get the mouse position and state(down or up). In this way you know if the user is dragging the green area and calculate DXX and SXX.
draw three rectangles with FillRect(): from 0 to DXX with picturebox back color, from DXX to SXX with green color and from SXX to the end with picturebox back color to an in memory dc eg hdcMemBackground
draw the grid lines to hdcMemBackground
Use the Point array and the polyline method i told you and in every loop move all your 999 points in the array one place to the left and add one point in the end of the array. To achieve this fill the array once before the infinite loop and inside it do the previous method
BitBlt hdcMemBackground to picturebox dc
Application::DoEvents();
EDIT (some code)
Create your resources once, when form loads, and release them in the end. Your Do_Chan()
creates considerable memory leaks. At form load:
HPEN hLinePenRed = NULL, hLinePenBlack = NULL, hLinePenWhite = NULL, hLinePenBlackDotted = NULL hPenOld; //Global
HBRUSH hBrushGreen = NULL, hBrushWhite = NULL, hBrushOld = NULL; //Global
HBITMAP hBitmap = NULL, hBitmapOld = NULL; //Global
HDC hdcMemBackground = NULL, hdcPicBox = NULL; //Global
//in form load event:
hLinePenRed = CreatePen(PS_SOLID, 1, RGB(255, 0, 0));
hLinePenBlack = CreatePen(PS_SOLID, 1, RGB(0, 0, 0));
hLinePenWhite = CreatePen(PS_SOLID, 1, RGB(245, 255, 250));
hLinePenBlackDotted = CreatePen(PS_DOT, 1, RGB(0, 0, 0));
hPenOld = SelectObject(hdcMemBackground, hLinePenRed);
hBrushGreen = CreateSolidBrush(RGB(166, 251, 178));
hBrushWhite = CreateSolidBrush(RGB(245, 255, 250));
hBrushOld = SelectObject(hdcMemBackground, hBrushGreen);
HDC hdc = CreateIC(TEXT("DISPLAY"), NULL, NULL, NULL);
hdcPicBox = GetWindowDC(hwndPicBox);
hdcMemBackground= CreateCompatibleDC(hdc);
hBitmap = CreateCompatibleBitmap(hdc, 1050, 550);
hBitmapOld = SelectObject(hdcMemBackground, hBitmap);
DeleteDC(hdc);
In the end when form closes:
SelectObject(hdcMemBackground, hPenOld);
DeleteObject(hLinePenRed);
DeleteObject(hLinePenBlack);
DeleteObject(hLinePenBlackDotted);
DeleteObject(hLinePenWhite);
SelectObject(hdcMemBackground, hBitmapOld);
DeleteObject(hBitmap);
SelectObject(hdcMemBackground, hBrushOld);
DeleteObject(hBrushGreen);
DeleteObject(hBrushWhite);
DeleteDC(hdcMemBackground);
ReleaseDC(hwndPicBox, hdcPicBox);
How to use FillRect and draw ellipses:
RECT rt;
rt.left = 0; rt.top = 0; rt.right = 1050; rt.bottom = 550;
FillRect(hdcMemBackground, &rt, hBrushWhite);
rt.left = DXX; rt.top = 50; rt.right = SXX; rt.bottom = 550;
FillRect(hdcMemBackground, &rt, hBrushGreen);
SelectObject(hdcMemBackground, hBrushGreen);
SelectObject(hdcMemBackground, hLinePenWhite);
Ellipse(hdcMemBackground, dx-10, y-20, dx+10, y);
Ellipse(hdcMemBackground, dx-10+spawn/2, y-20, dx+10+spawn/2, y);
Ellipse(hdcMemBackground, dx-10+spawn, y-20, dx+10+spawn, y);
//Plot the axis and the grid first and then draw the dotted vertical line
SelectObject(hdcMemBackground, hLinePenBlackDotted);
MoveToEx(hdcMemBackground, dx+spawn/2, 50, NULL);
LineTo(hdcMemBackground, dx+spawn/2, 550);
How to find mouse position and mouse state. This code will be at the beginning of each
iteration to see if user dragged the green area and calculate the new DXX, SXX:
/* It is buggy. My mistake
POINT pt;
GetCursorPos(&pt);
ScreenToClient(hwndPicBox, &pt);
if( pt.x >= 0 && pt.x <= picBoxWidth && pt.y >= 0 && pt.y <= picBoxHeight && (GetAsyncKeyState(VK_LBUTTON) & 0x8000) ){ //the mouse is down and inside picturebox
//do your staff
}
*/
Use instead picturebox mouse down, mouse up and mouse move events:
int isScrollingLeft = false; //global, the left circle
int isScrollingRight = false; //global, the right circle
int isScrollingMiddle = false; //global, the middle circle
System::Void Form1::pictureBox1_MouseDown(....){
//check if e.X and e.Y is inside in one of the three circles and set the
//appropriate isScrolling to true
}
System::Void Form1::pictureBox1_MouseMove(....){
if(isScrollingLeft){
//calculate DXX
}
else if(isScrollingRight){
//calculate SXX
}
else if(isScrollingMiddle){ //if you dont scroll this you dont need it
//
}
else{;} //do nothing
}
System::Void Form1::pictureBox1_MouseUp(....){
isScrollingLeft = false;
isScrollingRight = false;
isScrollingMiddle = false; //if you dont scroll this you dont need it
}
The way to move the points one place to the left:
POINT arrayPnt[1000]; //the array of points to be drawn by Polyline()
//the movement
memmove(&arrayPnt[0], &arrayPnt[1], 999 * sizeof(POINT));
//set the last one
arrayPnt[999].x = X;
arrayPnt[999].y = Y;
//Draw the lines
Polyline(hdcMemBackground, &arrayPnt, 1000);
To draw the number i into the label:
HDC hdcLabel1 = NULL; //global
HFONT hFont = NULL, hFontOld = NULL; //global
RECT rtLabel = NULL; //global
char strLabel1[5]; //global
Initialize once at the beggining like everything else
hdcLabel1 = GetWindowDC(label1Hwnd);
SetBkColor(hdcLabel1, RGB(?, ?, ?)); //i believe you use the color of your form
SetTextColor(hdcLabel1, RGB(255, 255, 255));
hFont = CreateFont(21, 0, 0, 0, /* Bold or normal*/FW_NORMAL, /*italic*/0, /*underline*/0, 0, ANSI_CHARSET, OUT_DEFAULT_PRECIS,
CLIP_DEFAULT_PRECIS, DEFAULT_QUALITY, DEFAULT_PITCH | FF_SWISS, TEXT("Arial")); //21 is i believe the 16 size in word
hFontOld = SelectObject(hdcLabel1, hFont);
rtLabel.top = 0; rtLabel.left = 0;
rtLabel.right = label1.Width; rtLabel.bottom = label1.Height;
and in the for loop draw the string into the label1
sprintf(strLabel1, "%d", i); //it is toooo slow. I have to think something better
DrawTextEx(hdcLabel1, strLabel1, -1, &rtLabel, DT_VCENTER | DT_SINGLELINE | DT_LEFT, NULL);
In the end ofcource release resources
SelectObject(hdcLabel1, hFontOld);
DeleteObject(hFont);
hFont = NULL;
ReleaseDC(label1Hwnd, hdcLabel1);
If you have any problems do comment.
valter
I got that code to get the pixel color from current mouse position.
It works well but the only problem is, I can't get it from an d3d application...
I tried it few times, but it only get only black color -
Red: 0
Green: 0
Blue: 0
Here's my code -
#include <stdio.h>
#include <stdlib.h>
#include <windows.h>
#include <d3d9.h>
HWND hWindow;
HDC hScreen;
HDC hdcMem;
HBITMAP hBitmap;
HGDIOBJ hOld;
int sX, sY, x, y;
BYTE* sData = 0;
POINT cursorPos;
int main()
{
int Red, Green, Blue;
hScreen = GetDC(hWindow);
sX = GetDeviceCaps(hScreen, HORZRES);
sY = GetDeviceCaps(hScreen, VERTRES);
hdcMem = CreateCompatibleDC (hScreen);
hBitmap = CreateCompatibleBitmap(hScreen, sX, sY);
BITMAPINFOHEADER bm = {0};
bm.biSize = sizeof(BITMAPINFOHEADER);
bm.biPlanes = 1;
bm.biBitCount = 32;
bm.biWidth = sX;
bm.biHeight = -sY;
bm.biCompression = BI_RGB;
bm.biSizeImage = 0; // 3 * sX * sY;
while (1) {
hOld = SelectObject(hdcMem, hBitmap);
BitBlt(hdcMem, 0, 0, sX, sY, hScreen, 0, 0, SRCCOPY);
SelectObject(hdcMem, hOld);
free(sData);
sData = (BYTE*)malloc(4 * sX * sY);
GetDIBits(hdcMem, hBitmap, 0, sY, sData, (BITMAPINFO*)&bm, DIB_RGB_COLORS);
GetCursorPos(&cursorPos);
x = cursorPos.x;
y = cursorPos.y;
Red = sData[4 * ( (y * sX) + x) +2];
Green = sData[4 * ( ( y * sX) + x) +1];
Blue = sData[4 * ( (y * sX) + x)];
printf("\nRed: %d\nGreen: %d\nBlue: %d\n", Red, Green, Blue);
Sleep(300);
}
}
Thanks!
Which kind of d3d application do you use? if the application use an Overlay surface, you can't get anything with code above. Overlay surface is widely used in Video players, it's totally different with normal surfaces in DirectX, the normal screen shot software can only catch data from primary surface, and Microsoft didn't provide any public interface to get data from Overlay surfaces, but some software can do this, the most common way is to hook DirectX, that's a different topic.
If your d3d application didn't use Overlay surface, you can use DiretX to get the data from screen, then get the pixel from the screen data you want.
Use CreateOffscreenPlainSurface to create an offscreen surface
Use GetFrontBufferData to get the data from screen
Lock the surface and read the pixel to get the color