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  • How to paint fully transparent pixels/points in P2D mode?

    - by netzwerg
    According to the Processing Reference, stroke(gray, alpha) allows to set the color and opacity of the stroke. With the default color mode, an alpha value of 255 denotes full opacity, while a value of 0 should correspond to complete transparency. While this works with the (default) JAVA2D renderer, I can't seem to paint fully transparent points in P2D mode. This code clearly renders a pixel at the center of the canvas, even though the alpha value is set to 0 (fully transparent): public class Transparency extends PApplet { @Override public void setup() { size(200, 200, P2D); } @Override public void draw() { stroke(0, 0); point(width / 2, height / 2); } public static void main(String[] args) { PApplet.main(new String[] { Transparency.class.getSimpleName() }); } } What's wrong here?

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  • HowTo set Icon to Qt Application, created with Qt Visual Studio Add-in?

    - by mosg
    Hello. Here is what I have: Visual Studio 2008 (on 32-bit Windows XP) Qt libraries 4.6.2 for Windows (VS 2008, 194 MB) Visual Studio Add-in (44 MB) After I installed all the software, I created simple Qt Application project, with Visual Studio: menu File | New | Project... and Qt4 Projects | Qt Application. Build it, and here is the question: how to set application icon to my compiled exe file? I need to see specified ICO in explorer! Old method with MyProject.pro not interested!!! Create a .ico file with both 16x16 and 32x32-pixel versions of the icon (you can do this in Visual Studio). Create a .rc file containing the following text: IDI_ICON1 ICON DISCARDABLE "myIcon.ico" Add the following to your .pro file RC_FILE = myFile.rc Run qmake. Thanks.

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  • Kink detection in drawn polylines

    - by David Rutten
    Users can sketch in my app using a very simple tool (move mouse while holding LMB). This results in a series of mousemove events and I record the cursor location at each event. The resulting polyline curve tends to be rather dense, with recorded points almost every other pixel. I'd like to smooth this pixelated polyline, but I don't want to smooth intended kinks. So how do I figure out where the kinks are? The image shows the recorded trail (red pixels) and the 'implied' shape as a human would understand it. People tend to slow down near corners, so there is usually even more noise here than on the straight bits.

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  • [C#] GrayScale (by ColorMatrix) causes OutOfMemoryException. Why ?

    - by Tony
    I have 2 forms, A and B. On the Form A, I click a button and an Image is being loaded to a PictureBox located ona the Form B. And, I want to set GrayScale to this image by: public void SetGrayScale(PictureBox pb) { ColorMatrix matrix = new ColorMatrix(new float[][] { new float[] {0.299f, 0.299f, 0.299f, 0, 0}, new float[] {0.587f, 0.587f, 0.587f, 0, 0}, new float[] {0.114f, 0.114f, 0.114f, 0, 0}, new float[] { 0, 0, 0, 1, 0}, new float[] { 0, 0, 0, 0, 0} }); Image image = (Bitmap)pb.Image.Clone(); ImageAttributes attributes = new ImageAttributes(); attributes.SetColorMatrix(matrix); Graphics graphics = Graphics.FromImage(image); graphics.DrawImage(image, new Rectangle(0, 0, image.Width, image.Height), 0, 0, image.Width, image.Height, GraphicsUnit.Pixel, attributes); graphics.Dispose(); pb.Image = image; } This code works properly when the PictureBox is on the same form (A). But, when it is on the Form B, the OutOfMemoryException is raised. Why ?

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  • ctypes and pointer manipulation

    - by Chris
    I am dealing with image buffers, and I want to be able to access data a few lines into my image for analysis with a c library. I have created my 8-bit pixel buffer in Python using create_string_buffer. Is there a way to get a pointer to a location within that buffer without re-creating a new buffer? My goal is to analyze and change data within that buffer in chunks, without having to do a lot of buffer creation and data copying. In this case, ultimately, the C library is doing all the manipulation of the buffer, so I don't actually have to change values within the buffer using Python. I just need to give my C function access to data within the buffer.

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  • iPhone image distortion

    - by Corey Floyd
    Are there any reasons why the simulator will display UIImageViews properly, but incorrectly on the iPhone? My Process: An image in a PNG file Start a UIGraphicsBeginImageContext() Draw the PNG in a CGrect Draw text in the CGRect Create an UIImage from the context Set the image of a UIImaveView to the UIImage Set the frame of the UIImageView to the size of the PNG Add as a subview Outcome: The image does not display correctly. The rightmost 1-3 pixels of the image is just a vertical white line. This occurs only on the device and not on the simulator. I can fix the problem, but only by increasing the size of the UIImageView. If I increase the size.height of the UIImageView by 1 pixel, it displays the UIImage correctly. Of course, these leaves the iPhone to scale my image before drawing it on screen which is not desirable. Any ideas why this occurs or any fixes for it? (I will post my code if needed)

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  • How to read and modify the colorspace of an image in c#

    - by Matthias
    I'm loading a Bitmap from a jpg file. If the image is not 24bit RGB, I'd like to convert it. The conversion should be fairly fast. The images I'm loading are up to huge (9000*9000 pixel with a compressed size of 40-50MB). How can this be done? Btw: I don't want to use any external libraries if possible. But if you know of an open source utility class performing the most common imaging tasks, I'd be happy to hear about it. Thanks in advance.

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  • Video Synthesis - Making waves, patterns, gradients...

    - by Nathan
    I'm writing a program to generate some wild visuals. So far I can paint each pixel with a random blue value: for (y = 0; y < YMAX; y++) { for (x = 0; x < XMAX; x++) { b = rand() % 255; setPixelColor(x,y,r,g,b); } } I'd like to do more than just make blue noise, but I'm not sure where to start (Google isn't helping me much today), so it would be great if you could share anything you know on the subject or some links to related resources.

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  • UITableView: moving a row into an empty section

    - by Frank C
    I have a UITableView with some empty sections. I'd like the user to be able to move a row into them using the standard edit mode controls. The only way I can do it so far is to have a dummy row in my "empty" sections and try to hide it by using tableView:heightForRowAtIndexPath: to give the dummy row a height of zero. This seems to leave it as a 1-pixel row. I can probably hide this by making a special type of cell that's just filled with [UIColor groupTableViewBackgroundColor], but is there a better way? This is all in the grouped mode of UITableView UPDATE: Looks like moving rows into empty sections IS possible without any tricks, but the "sensitivity" is bad enough that you DO need tricks in order to make it usable for general users (who won't be patient enough to slowly hover the row around the empty section until things click)

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  • In a digital photo, detecting if a mountain is obscured by clouds.

    - by Gavin Brock
    The problem I have a collection of digital photos of a mountain in Japan. However the mountain is often obscured by clouds or fog. What techniques can I use to detect that the mountain is visible in the image? I am currently using Perl with the Imager module, but open to alternatives. All the images are taken from the exact same position - these are some samples. My naïve solution I started by taking several horizontal pixel samples of the mountain cone and comparing the brightness values to other samples from the sky. This worked well for differentiating good image 1 and bad image 2. However in the autumn it snowed and the mountain became brighter than the sky, like image 3, and my simple brightness test started to fail. Image 4 is an example of an edge case. I would classify this as a good image since some of the mountain is clearly visible.

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  • On-the-fly lossless image compression

    - by geschema
    I have an embedded application where an image scanner sends out a stream of 16-bit pixels that are later assembled to a grayscale image. As I need to both save this data locally and forward it to a network interface, I'd like to compress the data stream to reduce the required storage space and network bandwidth. Is there a simple algorithm that I can use to losslessly compress the pixel data? I first thought of computing the difference between two consecutive pixels and then encoding this difference with a Huffman code. Unfortunately, the pixels are unsigned 16-bit quantities so the difference can be anywhere in the range -65535 .. +65535 which leads to potentially huge codeword lengths. If a few really long codewords occur in a row, I'll run into buffer overflow problems.

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  • image scaling with C

    - by sa125
    Hi - I'm trying to read an image file and scale it by multiplying each byte by a scale its pixel levels by some absolute factor. I'm not sure I'm doing it right, though - void scale_file(char *infile, char *outfile, float scale) { // open files for reading FILE *infile_p = fopen(infile, 'r'); FILE *outfile_p = fopen(outfile, 'w'); // init data holders char *data; char *scaled_data; // read each byte, scale and write back while ( fread(&data, 1, 1, infile_p) != EOF ) { *scaled_data = (*data) * scale; fwrite(&scaled_data, 1, 1, outfile); } // close files fclose(infile_p); fclose(outfile_p); } What gets me is how to do each byte multiplication (scale is 0-1.0 float) - I'm pretty sure I'm either reading it wrong or missing something big. Also, data is assumed to be unsigned (0-255). Please don't judge my poor code :) thanks

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  • Cross domain cookie tracking

    - by Jon
    Hi, The company I work for has four domains and I'm trying to set up the cookies, so one cookie can be generated and tracked across all the domains. From reading various posts on here I thought it was possible. I've set up a sub domain on one site, to serve a cookie and 1*1 pixel image to all four sites. But I can't get this working on the other sites. If anyone can clarify that: Its possible? If I'm missing something obvious or a link to a good example? I'm trying to do this server side with PHP. Thanks

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  • How to spin an independent dispacher thread for a Silverlight UserControl

    - by ondesertverge
    I am trying to move a lot of different elements by 1 pixel very often and in parallel. Trying to do this on one dispatcher thread means that the elements are visited one after another. The result is that the more elements I have the slower they will all move. In WPF I was able to use a HostVisual as described here to solve this. I can't seem to find anything similar in Silverlight. Is this a drawback of the lightweight framework or is there something I haven't stumbled upon yet? I am using SL4.

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  • Image 8-connectivity without excessive branching?

    - by shoosh
    I'm writing a low level image processing algorithm which needs to do alot of 8-connectivity checks for pixels. For every pixel I often need to check the pixels above it, below it and on its sides and diagonals. On the edges of the image there are special cases where there are only 5 or 3 neighbors instead of 8 neighbors for a pixels. The naive way to do it is for every access to check if the coordinates are in the right range and if not, return some default value. I'm looking for a way to avoid all these checks since they introduce a large overhead to the algorithm. Are there any tricks to avoid it altogether?

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  • Margin animate problem with Monitor display settings

    - by Jake
    I have an issue with an animation on a webpage. I have this div with text inside of it that I set the margin using css and when the page is loaded I use jquery to animate the div to a certain part of the page. The problem is it works with my concrete pixel settings, but if I change the properties of the monitor display settings in screen resolution(pixels), the div does not animate to the appropriate spot and it doesn't even start off at the appropriate spot from the css. Sample code: #div{ position:absolute; top:20px; left:50px } $("#div").animate({marginLeft: "250px"},2000); Is there a way to have the settings of the animation margin end at the approriate position no matter what the screen resolution is?

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  • Projecting a targetting ring using direct3d

    - by JohnB
    I'm trying to draw a "targetting ring" on the ground below a "unit" in a hobby 3d game I'm working on. Basically I want to project a bright red patterned ring onto the ground terrain below the unit. The only approach I can think of is this - Draw the world once as normal Draw the world a second time but in my vertex shader I have the world x,y,z coordinates of the vertex and I can pass in the coordinates of the highlighted unit - so I can calculate what the u,v coordinates in my project texture should be at that point in the world for that vertex. I'd then use the pixel shader to pick pixels from the target ring texture and blend them into the previously drawn world. I believe that should be easy, and should work but it involves me drawing the whole visible world twice as it's hard to determine exactly which polygons the targetting ring might fall onto. It seems a big overhead to draw the whole world twice, once for the normal lit textured ground, and then again just to draw the targetting ring. Is there a better approach that I'm missing?

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  • 8-direction path finding algorithm

    - by frinkz
    I'm having trouble finding the right pathfinding algorithm for some AI I'm working on. I have players on a pitch, moving around freely (not stuck to a grid), but they are confined to moving in 8 directions (N NE E etc.) I was working on using A*, and a graph for this. But I realised, every node on the graph is equally far apart, and all the edges have the same weight - since the pitch is rectangular. And the number of nodes is enormous (being a large pitch, with them able to move between 1 pixel and another) I figured there must be another algorithm, optimised for this sort of thing?

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  • Altering CSS for nav bar images to accomodate IE

    - by Kim
    My horizontal nav bar is populated with images for the links that are coming from one image that includes all the sub-images; each nav item image is identified by the pixel location within the larger image. This works perfectly fine in Firefox and Safari, but in IE, all of the images are misplaced too low within the nav bar (can only barely see the tops of the words). Two questions: How do I fix this in the css so it is back-compatible with the more recent versions (and current versions) of IE Do I need a separate IE stylesheet? Thanks!

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  • SSRS: Report loading external images, image not found, can I hide the image control

    - by Nauman
    My SSRS report loads logo images for each customer from a customer number specific folder on the report server. I write an expression, to form my URL to the image based on th customer number. ..."http://localhost/images/" + iCustomerNumber.ToString() + "/logo.gif" I am able to get this working, but the problem I face is, when a particular customer doesn't has an image, then my report shows a red X mark in place of the logo. In this case, I expect to hide the image control itself. Any thoughts???? The other dirty solution will be to ensure that each customer specific folder has the designated image! even if there is no logo for a customer, I'll place a blank.gif or a spacer.gif of probably a square pixel in dimension!.

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  • Why use multiple OpenGL context

    - by Luca
    For rendering I have a current GL context, associated to a window. In the case the application render multiple scenes (for example using accumulation or different viewports) I think it is ok to reuse the same context. My question, indeed, is: why should I use multiple GL context? I red on ARB_framebuffer_object extension spec that MakeCurrent call could be expansive, and in the case the ARB_framebuffer_object extension is present I can render on a generic buffer without using MakeCurrent. Apparently the only reason to use multiple GL context is to avoid to setup context state (pixel store, transfer, point size, polygon stipple...) or to have avaialable multiple render buffers configuration (one context with accumulation, another without). How to determine when is better an alternative context instead of setting context state? Thankyou all!

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  • Video Synthesis - Making waves, pattern, gradients...

    - by Nathan
    I'm writing a program to generate some trippy visuals. My code paints each pixel with a random blue value which loops at 0.04 second intervals. for (y = 0; y < 5.5; y += 0.2) { for (x = 0; x < 7.5; x += 0.2) { b = rand() / ((double) RAND_MAX); setPixelColor(x,y,r,g,b); } } I'd like to do more than just make blue noise... but my maths is a bit rusty, and Google isn't helping me much today, so it would be great if you could share anything you know about making waves, patterns, gradient animations, etc or links to such material.

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  • Three vertically stacked DIVs with scrolling middle

    - by Dave
    Is it possible to stack three DIVs vertically and have just the middle div scroll vertically? I don't want to use pixel heights, though, because the DIVs are inside of a dialog box that is resizeable. Something like this (pardon my lousy ASCII art): +-----------+ | Header | +-----------+ | ^| | || | Scroll || | || | v| +-----------+ | Footer | +-----------+ The goal is to have the header and and footer fixed and, as the dialog grows, the middle div would grow vertically. Maybe I'm just being stupid, but I've been fighting this for the last few hours and can't seem to get it right. The three DIVs probably need to be inside "another" DIV but when I do that, and set the height to 100%, it grows as the middle DIV grows. Again, it's probably something silly I'm not accounting for. I've also tried using a TABLE to no avail. Thanks for any help.

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  • OpenCV in Python can't scan through pixels

    - by Marco L.
    Hi everyone, I'm stuck with a problem of the python wrapper for OpenCv. I have this function that returns 1 if the number of black pixels is greater than treshold def checkBlackPixels( img, threshold ): width = img.width height = img.height nchannels = img.nChannels step = img.widthStep dimtot = width * height data = img.imageData black = 0 for i in range( 0, height ): for j in range( 0, width ): r = data[i*step + j*nchannels + 0] g = data[i*step + j*nchannels + 1] b = data[i*step + j*nchannels + 2] if r == 0 and g == 0 and b == 0: black = black + 1 if black >= threshold * dimtot: return 1 else: return 0 The loop (scan each pixel of a given image) works good when the input is an RGB image...but if the input is a single channel image I get this error: for j in range( width ): TypeError: Nested sequences should have 2 or 3 dimensions The input single channel image (called 'rg' in the next example) is taken from an RGB image called 'src' processed with cvSplit and then cvAbsDiff cvSplit( src, r, g, b, 'NULL' ) rg = cvCreateImage( cvGetSize(src), src.depth, 1 ) # R - G cvAbsDiff( r, g, rg ) I've also already noticed that the problem comes from the difference image got from cvSplit... Anyone can help me? Thank you

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  • Is there any simple way to test two PNGs for equality?

    - by Mason Wheeler
    I've got a bunch of PNG images, and I'm looking for a way to identify duplicates. By duplicates I mean, specifically, two PNG files whose uncompressed image data are identical, not necessarily whose files are identical. This means I can't do something simple like compare CRC hash values. I figure this can actually be done reliably since PNGs use lossless compression, but I'm worried about speed. I know I can winnow things down a little by testing for equal dimensions first, but when it comes time to actually compare the images against each other, is there any way to do it reasonably efficiently? (ie. faster than the "double-for-loop checking pixel values against each other" brute-force method?)

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