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CIE XYZ colorspace: do I have RGBA or XYZA?

- by Tronic

I plan to write a painting program based on linear combinations of xy plane points (0,1), (1,0) and (0,0). Such system works identically to RGB, except that the primaries are not within the gamut but at the corners of a triangle that encloses the entire gamut. I have seen the three points being referred to as X, Y and Z (upper case) somewhere, but I cannot find the page anymore (I marked them to the picture myself). My pixel format stores the intensity of each of those three components the same way as RGB does, together with alpha value. This allows using pretty much any image manipulation operation designed for RGBA without modifying the code. What is my format called? Is it XYZA, RGBA or something else? Google doesn't seem to know of XYZA. RGBA will get confused with sRGB + alpha (which I also need to use in the same program). Notice that the primaries X, Y and Z and their intensities have little to do with the x, y and z coordinates (lower case) that are more commonly used.

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GDI+ Rotated sub-image

- by Andrew Robinson

I have a rather large (30MB) image that I would like to take a small "slice" out of. The slice needs to represent a rotated portion of the original image. The following works but the corners are empty and it appears that I am taking a rectangular area of the original image, then rotating that and drawing it on an unrotated surface resulting in the missing corners. What I want is a rotated selection on the original image that is then drawn on an unrotated surface. I know I can first rotate the original image to accomplish this but this seems inefficient given its size. Any suggestions? Thanks, public Image SubImage(Image image, int x, int y, int width, int height, float angle) { var bitmap = new Bitmap(width, height); using (Graphics graphics = Graphics.FromImage(bitmap)) { graphics.TranslateTransform(bitmap.Width / 2.0f, bitmap.Height / 2.0f); graphics.RotateTransform(angle); graphics.TranslateTransform(-bitmap.Width / 2.0f, -bitmap.Height / 2.0f); graphics.DrawImage(image, new Rectangle(0, 0, width, height), x, y, width, height, GraphicsUnit.Pixel); } return bitmap; }

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Javascript/Canvas/Images scaling problem in Firefox

- by DocTiger

I have a problem with the context2d's drawImage function. Whenever I scale an image, it gets a dark border of one pixel, which is kind of ugly. That does only happen in Firefox, not in Opera or Webkit. Is this an antialiasing problem? For hours I studied the examples and available documentation without getting rid of it... I couldn't yet try it on another computer so maybe just maybe it's an issue with the graphics hardware/drivers. I have reproduced this effect with this minimal snippet, assuming exp.jpg is sized 200x200 pixels. <html> <body> <canvas id="canvas" width="400" height="400"></canvas> </body> <script type="text/javascript" src="../../media/pinax/js/jquery-1.3.2.min.js"></script> <script type="text/javascript" > context = $('#canvas')[0].getContext('2d'); img = new Image(); img.src = "exp.jpg"; //while (!img.complete); context.drawImage(img, 2,2,199,199); context.drawImage(img, 199,2,199,199); </script> </html>

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Inconsistent table width when hideing/showing a set of columns

- by Salman A. Kagzi

I have got a an HTML table of around 40+ columns. To make this table fit in the screen and have the data in a re presentable format we have section in this table. i.e. there are some column that are always visible and the remainder a made visible when s specific radio button (describing a section) is selected. Each radio button is associated to different number of columns. We show/hide a column by setting/removing "display:none" style in all the cell under that column. This all works Just fine. Now the real problem is with the width of the columns in this table. I cant use fixed with with pixel settings. I have tried using the percentage setting by giving 50% to the always visible part and rest 50% is divided between the column in a section. But I am unable to get a fixed behavior i.e. the size of the table columns across IE & FF. Some columns are just right while some are really huge. How can I get the table to give consistent column width across browsers?

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How to read time from recorded surveillance camera video?

- by stressed_geek

I have a problem where I have to read the time of recording from the video recorded by a surveillance camera. The time shows up on the top-left area of the video. Below is a link to screen grab of the area which shows the time. Also, the digit color(white/black) keeps changing during the duration of the video. http://i55.tinypic.com/2j5gca8.png Please guide me in the direction to approach this problem. I am a Java programmer so would prefer an approach through Java. EDIT: Thanks unhillbilly for the comment. I had looked at the Ron Cemer OCR library and its performance is much below our requirement. Since the ocr performance is less than desired, I was planning to build a character set using the screen grabs for all the digits, and using some image/pixel comparison library to compare the frame time with the character-set which will show a probabilistic result after comparison. So I was looking for a good image comparison library(I would be OK with a non-java library which I can run using the command-line). Also any advice on the above approach would be really helpful.

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How to optimize Conway's game of life for CUDA?

- by nlight

I've written this CUDA kernel for Conway's game of life: global void gameOfLife(float* returnBuffer, int width, int height) { unsigned int x = blockIdx.x*blockDim.x + threadIdx.x; unsigned int y = blockIdx.y*blockDim.y + threadIdx.y; float p = tex2D(inputTex, x, y); float neighbors = 0; neighbors += tex2D(inputTex, x+1, y); neighbors += tex2D(inputTex, x-1, y); neighbors += tex2D(inputTex, x, y+1); neighbors += tex2D(inputTex, x, y-1); neighbors += tex2D(inputTex, x+1, y+1); neighbors += tex2D(inputTex, x-1, y-1); neighbors += tex2D(inputTex, x-1, y+1); neighbors += tex2D(inputTex, x+1, y-1); __syncthreads(); float final = 0; if(neighbors < 2) final = 0; else if(neighbors 3) final = 0; else if(p != 0) final = 1; else if(neighbors == 3) final = 1; __syncthreads(); returnBuffer[x + y*width] = final; } I am looking for errors/optimizations. Parallel programming is quite new to me and I am not sure if I get how to do it right. The rest of the app is: Memcpy input array to a 2d texture inputTex stored in a CUDA array. Output is memcpy-ed from global memory to host and then dealt with. As you can see a thread deals with a single pixel. I am unsure if that is the fastest way as some sources suggest doing a row or more per thread. If I understand correctly NVidia themselves say that the more threads, the better. I would love advice on this on someone with practical experience.

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How can you transform a set of numbers into mostly whole ones?

- by Alice

Small amount of background: I am working on a converter that bridges between a map maker (Tiled) that outputs in XML, and an engine (Angel2D) that inputs lua tables. Most of this is straight forward However, Tiled outputs in pixel offsets (integers of absolute values), while Angel2D inputs OpenGL units (floats of relative values); a conversion factor between these two is needed (for example, 32px = 1gu). Since OpenGL units are abstract, and the camera can zoom in or out if the objects are too small or big, the actual conversion factor isn't important; I could use a random number, and the user would merely have to zoom in or out. But it would be best if the conversion factor was selected such that most numbers outputted were small and whole (or fractions of small whole numbers), because that makes it easier to work with (and the whole point of the OpenGL units is that they are easy to work with). How would I find such a conversion factor reliably? My first attempt was to use the smallest number given; this resulted in no fractions below 1, but often lead to lots of decimal places where the factors didn't line up. Then I tried the mode of the sequence, which lead to the largest number of 1's possible, but often lead to very long floats for background images. My current approach gets the GCD of the whole sequence, which, when it works, works great, but can easily be thrown off course by a single bad apple. Note that while I could easily just pass the numbers I am given along, or pick some fixed factor, or use one of the conversions I specified above, I am looking for a method to reliably scale this list of integers to small, whole numbers or simple fractions, because this would most likely be unsurprising to the end user; this is not a one off conversion. The end users tend to use 1.0 as their "base" for manipulations (because it's simple and obvious), so it would make more sense for the sizes of entities to cluster around this.

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Vehicle License Plate Detection

- by Ash

Hey all Basically for my final project at university, I'm developing a vehicle license plate detection application. Now I consider myself an intermediate programmer, however my mathematics knowledge lacks anything above secondary school, therefore producing detection formulae is basically impossible. I've spend a good amount of time looking up academic papers such as: http://www.scribd.com/doc/266575/Detecting-Vehicle-License-Plates-in-Images http://www.cic.unb.br/~mylene/PI_2010_2/ICIP10/pdfs/0003945.pdf http://www.eurasip.org/Proceedings/Eusipco/Eusipco2007/Papers/d3l-b05.pdf When it comes to the maths, I'm lost. Due to this testing various graphic images proved productive, for example: to However this approach is only catered to that particular image, and if the techniques were applied to different images, I'm sure a different, most likely poorer conversion would occur. I've read about a formula called the bottom hat morphology transform, which according to the first does the following: "Basically, the trans- formation keeps all the dark details of the picture, and eliminates everything else (including bigger dark regions and light regions)." Sadly I can't find much information on this, however the image within the documentation near the end of the report shows it's effectiveness. I'm aware this is complicated and vast, I'd just appreciate a little advice, even in terms of what transformation techniques I should focus on developing, or algorithm regarding edge detection or pixel detection. Few things I need to add Developing in C Sharp Confining the project to UK registration plates only I can basically choose the images to convert as a demonstration Thanks

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Moving UIScrollView in App

- by jsetting32

Currently, I am attempting to create the same effect as Yahoo! Weather's App where the vital day information is at the bottom of the page on the top of a UIScrollView, that's contained by a UIView. I am having a hard time thinking about how this is going to happen or how I should implement this. If the user taps on the top of the UIScrollView which is located near the bottom of the laoded UIView, and starts to scroll up (/), the UIScrollView's frame should be moved to the TOP of the current UIView's frame. So the UIScrollView's y-value should change to UIView's (self.view.frame.origin.y) if the user starts scrolling UP on the UIScrollView which is located on the UIView's y-pixel ~280. Here's what the UIViewController should look like in the beginning of loading the ViewController... Then once the user slides his finger from the bottom to the top of the screen... this should happen........ And when the user scrolls to the top of the UIScrollView with all the content within it... the view should go back to the start picture shown... How is this done? I was thinking several UIGestureRecognizer's and Instantiating the UIscrollview at the lower part of the UIView... _weatherView = [[UIScrollView alloc] initWithFrame:CGRectMake(self.view.frame.origin.x, self.view.frame.origin.y + 250, self.view.bounds.size.width, self.view.bounds.size.height - 44)]; _weatherView.contentSize = CGSizeMake(self.view.bounds.size.width, self.view.bounds.size.height * 4); _weatherView.backgroundColor = [UIColor clearColor]; [self.view addSubview:_weatherView]; The adding some UIGestureRecognizer delegate method.... But anyone have any ideas on the UIGestureRecognizer delegate method? And how it should be implemented? I can write the psuedo-code but I am having problems finding the delegate methods :P Thank you!!! ---- Break Time.... :)

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imageconvolution leaves black dot in the upper left corner

- by Peter O.

I'm trying to sharp resized images using this code: imageconvolution($imageResource, array( array( -1, -1, -1 ), array( -1, 16, -1 ), array( -1, -1, -1 ), ), 8, 0); When the transparent PNG image is sharpened, using code above, it appears with a black dot in the upper left corner (I have tried different convolution kernels, but the result is the same). After resizing the image looked OK. 1st image is the original one 2nd image is the sharpened one EDIT: What am I going wrong? I'm using the color retrieved from pixel. $color = imagecolorat($imageResource, 0, 0); imageconvolution($imageResource, array( array( -1, -1, -1 ), array( -1, 16, -1 ), array( -1, -1, -1 ), ), 8, 0); imagesetpixel($imageResource, 0, 0, $color); Is imagecolorat the right function? Or is the position correct? EDIT2: I have changed coordinates, but still no luck. I've check the transparency given by imagecolorat (according to this post). This is the dump: array(4) { red => 0 green => 0 blue => 0 alpha => 127 } Alpha 127 = 100% transparent. Those zeroes might cause the problem...

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VB.NET trying simple captcha

- by Pride Grimm

I'm trying to write a simple captcha program in vb.net. I'm just wanting to make an image from random numbers and display it, check the answer, and then proceed. I'm pretty new to vb.net, so I found some code to generate the information. I will cite the owner when I find it again (http://www.knowlegezone.com/80/article/Technology/Software/Asp-Net/Simple-ASP-NET-CAPTCHA-Tutorial) This is in the onload() of default2.aspx Public Sub returnNumer() Dim num1 As New Random Dim num2 As New Random Dim numQ1 As Integer Dim numQ2 As Integer Dim QString As String numQ1 = num1.Next(10, 15) numQ2 = num2.Next(17, 31) QString = numQ1.ToString + " + " + numQ2.ToString + " = " Session("answer") = numQ1 + numQ2 Dim bitmap As New Bitmap(85, 35) Dim Grfx As Graphics = Graphics.FromImage(bitmap) Dim font As New Font("Arial", 18, FontStyle.Bold, GraphicsUnit.Pixel) Dim Rect As New Rectangle(0, 0, 100, 50) Grfx.FillRectangle(Brushes.Brown, Rect) Grfx.DrawRectangle(Pens.PeachPuff, Rect) ' Border Grfx.DrawString(QString, font, Brushes.Azure, 0, 0) Response.ContentType = "Image/jpeg" bitmap.Save(Response.OutputStream, System.Drawing.Imaging.ImageFormat.Jpeg) bitmap.Dispose() Grfx.Dispose() End Sub So I put this in a separate page, like this This all works find and dandy, but when I get the answer from the session like this Dim literal As String = Convert.ToString(Session("answer")) It's always one behind. So if The images adds to 32, the answer in session isn't 32. But after a refresh (and a new image) the session("answer") will be 32. Is there a way to refresh the session on page 1, after the default2.aspx loads? Is there a better way to do this? I though about trying to run the code all on one page, and trying to set the src of and image to returnNumber(), but I need a bit of help on that one.

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RetinaJS and LESS : Background image doesn't show on iOS

- by jidma

I am trying to make a background image into a retina image using LESS CSS and RetinaJs: in my index.html file : <html> <head> <meta http-equiv="content-type" content="text/html; charset=UTF-8"> <meta name="viewport" content="width=device-width, initial-scale=1.0, user-scalable=0, minimum-scale=1.0, maximum-scale=1.0"> <meta name="apple-mobile-web-app-capable" content="yes"> <meta name="apple-mobile-web-app-status-bar-style" content="black"> [...] <link type="text/css" rel="stylesheet/less" href="resources/css/retina.less"> <script type="text/javascript" src="resources/js/less-1.3.0.minjs" ></script> [...] </head> <body> [...] <script type="text/javascript" src="resources/js/retina.js"></script> </body> </html> in my retina.less file: .at2x(@path, @w: auto, @h: auto) { background-image: url("@{path}"); @at2x_path: ~`"@{path}".split('.').slice(0, "@{path}".split('.').length - 1).join(".") + "@2x" + "." + "@{path}".split('.')["@{path}".split('.').length - 1]`; @media all and (-webkit-min-device-pixel-ratio : 1.5) { background-image: url("@{at2x_path}"); background-size: @w @h; } } .topMenu { .at2x('../../resources/img/topMenuTitle.png'); } I have both topMenuTitle.png (320px x 40px) and [email protected] (640px x 80px) in the same folder. When test this code: In Firefox i have the normal Background In the XCode iPhone simulator I also have the normal Background In the iPhone device, I don't have any background at all. I'm using GWT if that matters. Any suggestions ? Thanks.

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Where is the "ListViewItemPlaceholderBackgroundThemeBrush" located?

- by Dimi Toulakis

I have a problem understanding one style definition in Windows 8 metro apps. When you create a metro style application with VS, there is also a folder named Common created. Inside this folder there is file called StandardStyles.xaml Now the following snippet is from this file:  <DataTemplate x:Key="Standard250x250ItemTemplate"> <Grid HorizontalAlignment="Left" Width="250" Height="250"> <Border Background="{StaticResource ListViewItemPlaceholderBackgroundThemeBrush}"> <Image Source="{Binding Image}" Stretch="UniformToFill"/> </Border> <StackPanel VerticalAlignment="Bottom" Background="{StaticResource ListViewItemOverlayBackgroundThemeBrush}"> <TextBlock Text="{Binding Title}" Foreground="{StaticResource ListViewItemOverlayForegroundThemeBrush}" Style="{StaticResource TitleTextStyle}" Height="60" Margin="15,0,15,0"/> <TextBlock Text="{Binding Subtitle}" Foreground="{StaticResource ListViewItemOverlaySecondaryForegroundThemeBrush}" Style="{StaticResource CaptionTextStyle}" TextWrapping="NoWrap" Margin="15,0,15,10"/> </StackPanel> </Grid> </DataTemplate> What I do not understand here is the static resource definition, e.g. for the Border Background="{StaticResource ListViewItemPlaceholderBackgroundThemeBrush}" It is not about how you work with templates and binding and resources. Where is this ListViewItemPlaceholderBackgroundThemeBrush located? Many thanks for your help. Dimi

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Chrome targeted CSS

- by Chris

I have some CSS code that hides the cursor on a web page (it is a client facing static screen with no interaction). The code I use to do this is below: *, html { cursor: url('/web/resources/graphics/blank.cur'), pointer; } Blank.cur is a totally blank cursor file. This code works perfectly well in all browsers when I host the web files on my local server but when I upload to a Windows CE webserver (our production unit) the cursor represents itself as a black box. Odd. After some testing it seems that chrome only has a problem with totally blank cursor files when served from WinCE web server, so I created a blank cursor with one pixel as white, specifically for chrome. How do I then target this CSS rule to chrome specifically? i.e. *, html { cursor: url('/web/resources/graphics/blank.cur'), pointer; } 

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Formulae for U and V buffer offset

- by Abhi

Hi all ! What should be the buffer offset value for U & V in YUV444 format type? Like for an example if i am using YV12 format the value is as follows: ppData.inputIDMAChannel.UBufOffset = iInputHeight * iInputWidth + (iInputHeight * iInputWidth)/4; ppData.inputIDMAChannel.VBufOffset = iInputHeight * iInputWidth; iInputHeight = 160 & iInputWidth = 112 ppdata is an object for the following structure: typedef struct ppConfigDataStruct { //--------------------------------------------------------------- // General controls //--------------------------------------------------------------- UINT8 IntType; // FIRSTMODULE_INTERRUPT: the interrupt will be // rised once the first sub-module finished its job. // FRAME_INTERRUPT: the interrput will be rised // after all sub-modules finished their jobs. //--------------------------------------------------------------- // Format controls //--------------------------------------------------------------- // For input idmaChannel inputIDMAChannel; BOOL bCombineEnable; idmaChannel inputcombIDMAChannel; UINT8 inputcombAlpha; UINT32 inputcombColorkey; icAlphaType alphaType; // For output idmaChannel outputIDMAChannel; CSCEQUATION CSCEquation; // Selects R2Y or Y2R CSC Equation icCSCCoeffs CSCCoeffs; // Selects R2Y or Y2R CSC Equation icFlipRot FlipRot; // Flip/Rotate controls for VF BOOL allowNopPP; // flag to indicate we need a NOP PP processing }*pPpConfigData, ppConfigData; and idmaChannel structure is as follows: typedef struct idmaChannelStruct { icFormat FrameFormat; // YUV or RGB icFrameSize FrameSize; // frame size UINT32 LineStride;// stride in bytes icPixelFormat PixelFormat;// Input frame RGB format, set NULL // to use standard settings. icDataWidth DataWidth;// Bits per pixel for RGB format UINT32 UBufOffset;// offset of U buffer from Y buffer start address // ignored if non-planar image format UINT32 VBufOffset;// offset of U buffer from Y buffer start address // ignored if non-planar image format } idmaChannel, *pIdmaChannel; I want the formulae for ppData.inputIDMAChannel.UBufOffset & ppData.inputIDMAChannel.VBufOffset for YUV444 Thanks in advance

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How can I generate an "unlimited" world?

- by snowlord

I would like to create a game with an endless (in reality an extremely large) world in which the player can move about. Whether or not I will ever get around to implement the game is one matter, but I find the idea interesting and would like some input on how to do it. The point is to have a world where all data is generated randomly on-demand, but in a deterministic way. Currently I focus on a large 2D map from which it should be possible to display any part without knowledge about the surrounding parts. I have implemented a prototype by writing a function that gives a random-looking, but deterministic, integer given the x and y of a pixel on the map (see my recent question about this function). Using this function I populate the map with "random" values, and then I smooth the map using a simple filter based on the surrounding pixels. This makes the map dependent on a few pixels outside its edge, but that's not a big problem. The final result is something that at least looks like a map (especially with a good altitude color map). Given this, one could maybe first generate a coarser map which is used to generate bigger differences in altitude to create mountain ranges and seas. Anyway, that was my idea, but I am sure that there exist ways to do this already and I also believe that given the specification, many of you can come up with better ideas. EDIT: Forgot the link to my question.

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Cocos2d - smooth sprite movement in tile map RPG

- by Lendo92

I've been working on a 2-D Gameboy style RPG for a while now, and the game logic is mostly all done so I'm starting to try to make things look good. One thing I've noticed is that the walking movement / screen movement is a little bit choppy. Technically, it should work fine, but either it seems to be having some quirks, either due to taking up a lot of processing power or just timing inconsistencies between moving the screen and moving the sprite. To move the sprite, once I know where I want to move it, I call: tempPos.y += 3*theHKMap.tileSize.width/5; id actionMove = [CCMoveTo actionWithDuration:0.1 position:tempPos]; id actionMoveDone = [CCCallFuncN actionWithTarget:self selector:@selector(orientOneMove)]; [guy runAction:[CCSequence actions:actionMove, actionMoveDone, nil]]; [self setCenterOfScreen:position]; Then, in orientOneMove, I call: [self.guy setTexture:[[CCTextureCache sharedTextureCache] addImage:@"guysprite07.png"]]; //the walking picture-I change texture back at the end of the movement id actionMove = [CCMoveTo actionWithDuration:0.15 position:self.tempLocation2]; id actionMoveDone = [CCCallFuncN actionWithTarget:self selector:@selector(toggleTouchEnabled)]; [guy runAction:[CCSequence actions:actionMove, actionMoveDone, nil]]; The code for the concurrently running setCenterOfScreen:position method is: id actionMove = [CCMoveTo actionWithDuration:0.25 position:difference]; [self runAction: [CCSequence actions:actionMove, nil, nil]]; So the setCenterOfScreen moves the camera in one clean move while the guy moving is chopped into two actions to animate it (which I believe might be inefficient.) It's hard to tell what is making the movement not perfectly clean from looking at it, but essentially the guy isn't always perfectly in the center of the screen -- during movement, he's often times a pixel or two off for an instant. Any ideas/ solutions?

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Dynamic TextBox on LinkButton click

- by Alex Peta

I am creating dynamic TextBoxes in a page by clicking a LinkButton. However, after that, if the page is submitted, I can't find the items created dynamically, thus, can't send the information to the database. protected void lbAddTag_Click(object sender, EventArgs e) { for (int i = 0; i < 3;i++ ) { CreateTextBox("txtTag-" + i.ToString()); } } private void CreateTextBox(string ID) { TextBox txt = new TextBox(); txt.ID = ID; txt.Width = Unit.Pixel(300); //txt.TextChanged += new EventHandler(OnTextChanged); txt.AutoPostBack = false; tagsPanel.Controls.Add(txt); Literal lt = new Literal(); lt.Text = "<br /><br />"; tagsPanel.Controls.Add(lt); } If I put: foreach (Control c in tagsPanel.Controls) { if (c is TextBox) { lblError.Text += c.ClientID + " , "; } } in the lbAddTag_Click method I can see the items, and they exist, but if I submit the page and try to insert the values in the database nothing... Any hint is much appreciated.

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Move camera to fit 3D scene

- by Burre

Hi there. I'm looking for an algorithm to fit a bounding box inside a viewport (in my case a DirectX scene). I know about algorithms for centering a bounding sphere in a orthographic camera but would need the same for a bounding box and a perspective camera. I have most of the data: I have the up-vector for the camera I have the center point of the bounding box I have the look-at vector (direction and distance) from the camera point to the box center I have projected the points on a plane perpendicular to the camera and retrieved the coefficients describing how much the max/min X and Y coords are within or outside the viewing plane. Problems I have: Center of the bounding box isn't necessarily in the center of the viewport (that is, it's bounding rectangle after projection). Since the field of view "skew" the projection (see http://en.wikipedia.org/wiki/File:Perspective-foreshortening.svg) I cannot simply use the coefficients as a scale factor to move the camera because it will overshoot/undershoot the desired camera position How do I find the camera position so that it fills the viewport as pixel perfect as possible (exception being if the aspect ratio is far from 1.0, it only needs to fill one of the screen axis)? I've tried some other things: Using a bounding sphere and Tangent to find a scale factor to move the camera. This doesn't work well, because, it doesn't take into account the perspective projection, and secondly spheres are bad bounding volumes for my use because I have a lot of flat and long geometries. Iterating calls to the function to get a smaller and smaller error in the camera position. This has worked somewhat, but I can sometimes run into weird edge cases where the camera position overshoots too much and the error factor increases. Also, when doing this I didn't recenter the model based on the position of the bounding rectangle. I couldn't find a solid, robust way to do that reliably. Help please!

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Customizing the Stars Image for Ajaxful_Rating RoR plugin

- by Kevin

I'm trying to come up with my own star image that's slightly smaller and different style than the one provided in the gem/plugin, but Ajaxful_rating doesn't have an easy way to do this. Here's what I've figured out so far: The stars.png in the public folder is three 25x25 pixel tiles stacked vertically, ordered empty star, normal star, and hover star. I'm assuming as long as you keep the above constraints, you should be fine without modifying any other files. But what if you want to change the image size of the stars to larger or smaller? I've found where you can change the height in the stylesheets/ajaxful_rating.css .ajaxful-rating{ position: relative; /*width: 125px; this is setted dynamically */ height: 25px; overflow: hidden; list-style: none; margin: 0; padding: 0; background-position: left top; } .ajaxful-rating li{ display: inline; } .ajaxful-rating a, .ajaxful-rating span, .ajaxful-rating .show-value{ position: absolute; top: 0; left: 0; text-indent: -1000em; height: 25px; line-height: 25px; outline: none; overflow: hidden; border: none; } You just need to change every place that says "25px" above to whatever height your new star image is. This works fine but doesn't display the horizontal part correctly. Anyone know where I would look to set the horizontal part as well? (I'm assuming it's in an .rb file somewhere based upon how many stars you specified in your ajaxful_rating setup)

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iPhone: How to Determine Average Light/Dark of an Area of an UIImage

- by TechZen

I need to place labels with a transparent background over a variable-content UIImage. Readability will vary significantly depending on the relationship between the color of the label's text and the color/luminosity of the area of the image displayed under the label. Since the image will be constantly changing, the color of the label's text needs to change in sync. I have found several techniques for determining the color, perceived luminosity etc of a single pixel. However, I need to rather quickly (while a view loads) determine the rough perceived color/luminosity of an area of the UIImage under the frame of the UILabel. I presume I will also need to measure the alpha because the same color/luminosity looks different at different alpha values. Is there a way to calculate such a value for an area? Will I be reduced to simply summing pixels? If it comes to that, is there an algorithm to accomplish this? I've thought of two possible approaches: Perform some "folding" operations i.e. combining pixels from one half of the area to the other half. Then repeat until I get a single value. Would this be practical? How would you logically combine pixels to average their perceived color/luminosity? Sample a statistically significant number of pixels in the area and then combine them (somehow) to get a rough measure. I think this problem comes up a lot these days with people being so found of customizing backgrounds. Seems like something that would be worth my time to bang out a category or class to handle this and then share it around.

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Problem shrinking with StretchBlt()

- by SparkyNZ

Hi. I have some code that paints my own rectangular buttons based on a source bitmap. Most of the time the destination buttons are bigger than my source bitmap image and StretchBlt works fine. However, when the destination is smaller than the source image, StretchBlt refuses to fill the entire destination area. I know StretchBlt isn't great on quality when it comes to scaling down images but I'm not too concerned about that. I just don't want missing pixels. Here a link with the source image at the top and destination at the bottom: link text Note, I am actually shrinking parts of the source image into the destination. I am not shrinking the entire image down. So for example, I copy the corners size for size with BitBlt() then I stretch (squash) the horizontal pixel data between the corners from the source image into the destination DC. There is no fault with my source and destination coordinates. If I change from SRCCOPY to WHITENESS, the entire area fills with white as you'd expect. There is no grey bar where pixels haven't copied as you see in the Broken.bmp image above. Has anyone had this problem before, and if so, can somebody please suggest a solution? Cheers

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Simple binary File I/O problem with cstdio(c++)

- by Atilla Filiz

The c++ program below fails to read the file. I know using cstdio is not good practice but that what I am used to and it should work anyway. $ ls -l l.uyvy -rw-r--r-- 1 atilla atilla 614400 2010-04-24 18:11 l.uyvy $ ./a.out l.uyvy Read 0 bytes out of 614400, possibly wrong file code: #include<cstdio> int main(int argc, char* argv[]) { FILE *fp; if(argc<2) { printf("usage: %s <input>\n",argv[0]); return 1; } fp=fopen(argv[1],"rb"); if(!fp) { printf("erör, cannot open %s for reading\n",argv[1]); return -1; } int bytes_read=fread(imgdata,1,2*IMAGE_SIZE,fp); //2bytes per pixel fclose(fp); if(bytes_read < 2*IMAGE_SIZE) { printf("Read %d bytes out of %d, possibly wrong file\n", bytes_read, 2*IMAGE_SIZE); return -1; } return 0; }

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CSS3PIE issues in IE6 and 8

- by Gordon

I'm using CSS3PIE to apply some rounded corners to elements in Internet Explorer that will get them by stylesheet in other browsers. I've run into some issues with it though. In IE8, I discovered that any element that had the PIE behaviour would behave strangely. The container would jump a few pixels to the right, but the content would stay in its original position, giving the appearance that the content had all shifted left relative to its container. This would be especially problematic on elements with no or small amounts of padding. I was able to hack my way around the problem in IE8 by using X-UA-Compatible, but I'd rather avoid this solution if at all possible. I don't have access to IE9 for testing but my understanding hacks like PIE aren't necessary and it would be wasteful to force a compatibility mode in a browser that doesn't need it. I have worse issues in IE6, with the PIE layout breaking down completely on a list that is set up to use display:inline; zoom:1; list items (to simulate inline-block, which works in IE8 and the other browsers). Here the borders of the list items get rendered in completely the wrong place. So ideally, I'd like to have PIE work properly in IE6, and in IE8 without having to resort to compatibility mode. As far as IE6 goes, a graceful fallback where PIE is just not applied will do. IE7 is the only browser where the page displays as intended. I can't provide an example page just at the moment unfortunately, I can add one later though. Follow up: Here are some screen grabs made with IE Tester. I'm hoping they will make things a little more clear for everybody. As you can see, IE7 is fine. However, in IE8, the containers are offset to the left relative to their content, and in IE6 the list elements (with the rounded 1 pixel border) are a complete mess! Full size versions for IE8, IE7 and IE6 are also available

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Canvas Check before submission

- by smokinguns

I have a page where a user can draw on the canvas and save the image to a file on the server. The canvas has a default black background. Is there a way to check if the user has drawn anything on the canvas before submitting the data URL representation of the image of a canvas with the toDataURL() function? So if the user doesn't draw anything on the canvas(it will be a blank canvas with a black background), the image wont be created on the server. Should I loop through each and every pixel of the canvas to determine this? Here is what I'm doing currently: var currentPixels = context.getImageData(0, 0, 600, 400); for (var y = 0; y < currentPixels.height; y += 1) { for (var x = 0; x < currentPixels.width; x += 1) { for (var c = 0; c < 3; c += 1) { var i = (y*currentPixels.width + x)*4 + c; if(currentPixels.data[i]!=0) break; } } }

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