I've started SDL just a few days ago and I'm having a problem
I tried to erase an image from the screen and replace it with the new one
here is my logic :
load image
apply surface, then delay for 1s
free old image surface (SDL_FreeSurface())
load new image
apply surface
The problem is the image is still there. (it didn't get erased, just stacked with the new image)
The screen doesn't work like you think it does. You cannot "delete" something from a screen buffer, you can only write new things to the screen buffer. To 'erase' something you need to write the "background" over it.
Some game loops just re-write the entire screen with the background every frame.
This probably belongs over at gamedev.stackexchange.com
Related
I am relatively new to OpenCV. My program will have a fixed camera that will track insects moving passed it. I figured that this would mean that I could remove the background from the video. I have attempted to use the method (which I found in a tutorial - http://docs.opencv.org/3.1.0/d1/dc5/tutorial_background_subtraction.html#gsc.tab=0):
pMOG2 = cv::createBackgroundSubtractorMOG2();
..
pMOG2->apply(frame, background);
However, how does this determine the background?
I have tried another way, which I thought might work, which was to capture the background when the program first starts and then use absDiff() or subtraction() on the background and current frame. Unfortunately, this results in a strange image which has parts of the static background image displayed over the video, this messes up the tracking.
I am a bit confused as to what would be the best way to do things. Is it possible to remove a specific background from each frame?
Thanks!
I am currently using the 16-bit libnds (Whith devkitpro) example as a basis and am trying to display text and the png background image on the same screen (in this example it is the top sceen). I am having a similar issue as this post.
I have garbage on the top of the screen (only ifconsoleInit(...) is called), similar to the first problem in the thread. The only problem is that I am displaying the background image in a different method so the fixes they made in that thread did not apply to this.
All I am looking for is whether there is a way to fix the garbage on the top of the screen. If there is a more efficient/better way to display the image, I am willing to accept it, just I haven't found a detailed enough tutorial on how to load an image as a background without using this method. Any help would be appreciated. I will answer any further questions anyone has about what is not working.
You can find the project attached here.
Sorry for the long delay but there are a few issues with your code. The first is that in Mode 4 the only background that can be set up as a 16 bit bitmap is layer 3. http://answers.drunkencoders.com/what-graphics-modes-does-the-ds-support/
Next, the layers all share a single chunk of background memory and your garbage is coming from you overwriting part of the bitmap in video memory with the characters for the font and the map for the console background. A simple solution is to move the bitmap by settings its map base to 1. This offsets its in graphics memory by 16KB which leaves 16KB of room for your text layer (this only works because we cant display the entire 256x256 image on screen at once due the the resolution of the DS as 256x256x2bytes fills up all of memory bank A...to be more correct we should assign another memory bank to the main background...but since we cant see the bottom 70 or so lines of pixels of our image anyway its okay that they didnt quite make it into video memory).
libnds also has a macro to make finding the memory for your background a bit simpler called "bgGetGfxPtr(id)" which will get a pointer to your background gfx in video memory after you set it up so you dont have to try to calculate it via an offset from BG_GFX.
In all the changes to your code should look like this (I added a version of this to the libnds code faq at : http://answers.drunkencoders.com/wp-admin/post.php?post=289&action=edit&message=1)
int main(void) {
//Top screen pic init
videoSetMode(MODE_4_2D);
vramSetBankA(VRAM_A_MAIN_BG);
int bg = bgInit(3, BgType_Bmp16, BgSize_B16_256x256, 1,0);
decompress(drunkenlogoBitmap, bgGetGfxPtr(bg), LZ77Vram); //Displays/decompresses top image
//videoSetMode(MODE_4_2D);
consoleInit(0,0, BgType_Text4bpp, BgSize_T_256x256, 4,0, true, true);
iprintf("\x1b[1;1HThe garbage is up here ^^^^^.");
iprintf("\x1b[21;1HTesting the text function...");
while(1) {
swiWaitForVBlank();
scanKeys();
if (keysDown()&KEY_START) break;
}
return 0;
}
I have to display an image and text overlay, when text overlay contains many strings, but only one changes from frame to frame. I want to avoid redraw of the entire overlay and only update what has changed.
I tried wglCreateLayerContext but my GPU seems to not support it (PIXELFORMATDESCRIPTOR bReserved is 0).
What is the most efficient way to redraw only part of text overlay?
Redrawing the whole framebuffer is the canonical way in OpenGL. You can use Framebuffer Objects (FBO) to create several off-screen drawing surfaces, to which you render the individual layers. Then you composit the layers into a composite image presented on screen.
but only one changes from frame to frame. I want to avoid redraw of the entire overlay
Why? Figuring out what parts need redraw, masking them, do only a partial clear, updating it, etc. takes more time and effort than to simply redraw the whole text overlay.
I am using SetPixel(GetDC(0),x,y,color) to write on the screen but as I do that, some other program updates it's screen and overwrites my drawn pixel thus the image drawn on screen appear to sparkle.
How Can I avoid this and draw something on the screen without the fear that it will be overwritten?
The screen is a shared resource. If you want something that is exclusively yours, create a window and draw into that.
I am developing a game where I need to reload scenes many times.
What I decided to do is when I finish each level to clear my current scene, create another "buffer" scene and then reload the first one (after having cleared my memory).
The problem is that after I get from the buffer scene to the last one, a black screen appears. In the console I can see that the last scene was loaded and initiated correctly but still nothing appears..
Any ideas?
Thank you for your help!!!