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  • WPF zoom canvas and maintain scroll position

    - by Alex McBride
    I have a Canvas element, contained within a ScrollViewer, which I'm zooming using ScaleTransform. However, I want to be able to keep the scroll position of the viewer focused on the same part of the canvas after the zoom operation has finished. Currently when I zoom the canvas the scroll position of the viewer stays where it was and the place the user was viewing is lost. I'm still learning WPF, and I've been going backwards and forwards a bit on this, but I can't figure out a nice XAML based way to accomplish what I want. Any help in this matter would be greatly appreciated and would aid me in my learning process. Here is the kind of code I'm using... <Grid> <ScrollViewer Name="TrackScrollViewer" HorizontalScrollBarVisibility="Auto" VerticalScrollBarVisibility="Auto"> <Canvas Width="2560" Height="2560" Name="TrackCanvas"> <Canvas.LayoutTransform> <ScaleTransform ScaleX="{Binding ElementName=ZoomSlider, Path=Value}" ScaleY="{Binding ElementName=ZoomSlider, Path=Value}"/> </Canvas.LayoutTransform> <!-- Some complex geometry describing a motor racing circuit --> </Canvas> </ScrollViewer> <StackPanel Orientation="Horizontal" Margin="8" VerticalAlignment="Top" HorizontalAlignment="Left"> <Slider Name="ZoomSlider" Width="80" Minimum="0.1" Maximum="10" Value="1"/> <TextBlock Margin="4,0,0,0" VerticalAlignment="Center" Text="{Binding ElementName=ZoomSlider, Path=Value, StringFormat=F1}"/> </StackPanel> </Grid>

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  • Making Firefox render canvas text the same as CSS text

    - by Dan Forys
    I've been experimenting with the canvas tag and Javascript. I've made a page that takes Tweets from the Twitter public timeline and animates them into view. It works by using a canvas element in the background for the animation. When the animation is complete, it creates a div element with the same text over the top. I do this so that the tweet text is selectable and links are clickable. Now, in Safari, Chrome and even Opera, the canvas text and div text look almost exactly the same. Yet in Firefox, the size of the text is different enough to make it 'jump' at the point it changes into the div. Does anyone know how to make Firefox render the text the same on the canvas element and the div using CSS? Or is this a rendering inconsistency with the engine. I have put the page on my website if you want to see what I mean. Now for the code: The CSS I'm using for rendering the div contains: line-height: 21px; font-weight: 100; font-family: Georgia, "New Century Schoolbook", "Nimbus Roman No9 L", serif; font-size: 20px; For rendering on the canvas I'm using: this.context.font = this.scale + 'px Georgia'; this.context.fillStyle = "white"; this.context.strokeStyle = 'white'; this.context.fillText(this.text, 0, 0); this.context.strokeText(this.text, 0, 0); where this.scale is an animated scale factor that finishes at 20px exactly. So, to recap, I'm using the same font and ending up at the same px size, yet Firefox renders the text differently between Canvas and CSS. (edit) Here's a screenshot example: First line is the text animating in using canvas, second line is the resulting div.

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  • C# XAML get new width and height for Canvas

    - by Jack Navarro
    I have searched through many times but have not seen this before. Probably really simple question but can't wrap my head around it. Wrote a VSTO add-in for Excel that draws a Grid dynamically. Then launches a new window and replaces the contents of the Canvas with the generated Grid. The problem is with printing. When I call the print procedure the canvas.height and canvas.width returned is the old value prior to replacing it with the grid. Sample: string="<Grid Name=\"CanvasGrid\" xmlns=\"http://schemas.microsoft.com/winfx/2006/xaml/presentation\">..Lots of stuff..</Grid>"; // Launch new window and replace the Canvas element WpfUserControl newWindow = new WpfUserControl(); newWindow.Show(); //To test MessageBox.Show(myCanvas.ActualWidth.ToString()); //return 894 Grid testGrid = myCanvas.FindName("CanvasGrid") as Grid; MessageBox.Show("Grid " + testGrid.ActualWidth.ToString()); //return 234 StringReader stringReader = new StringReader(LssAllcChrt); XmlReader xmlReader = XmlReader.Create(stringReader); Canvas myCanvas = newWindow.FindName("GrphCnvs") as Canvas; myCanvas.Children.Clear(); myCanvas.Children.Add((UIElement)XamlReader.Load(xmlReader)); //To test MessageBox.Show(myCanvas.ActualWidth.ToString()); //return 894 but should be much larger the Grid spans all three of my screens Grid testGrid = myCanvas.FindName("CanvasGrid") as Grid; MessageBox.Show("Grid " + testGrid.ActualWidth.ToString()); //return 234 but should be much larger the Grid spans all three of my screens //Run code from WpfUserControl.cs after it loads from button click Grid testGrid = canvas.FindName("CanvasGrid") as Grid; MessageBox.Show("Grid " + testGrid.ActualWidth.ToString()); //return 234 but should be much larger the Grid spans all three of my screens So basically I have no way of telling what my new width and height are Any Ideas

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  • XAML get new width and height for Canvas

    - by Jack Navarro
    I have searched through many times but have not seen this before. Probably really simple question but can't wrap my head around it. Wrote a VSTO add-in for Excel that draws a Grid dynamically. Then launches a new window and replaces the contents of the Canvas with the generated Grid. The problem is with printing. When I call the print procedure the canvas.height and canvas.width returned is the old value prior to replacing it with the grid. Sample: string="<Grid Name=\"CanvasGrid\" xmlns=\"http://schemas.microsoft.com/winfx/2006/xaml/presentation\">..Lots of stuff..</Grid>"; // Launch new window and replace the Canvas element WpfUserControl newWindow = new WpfUserControl(); newWindow.Show(); //To test MessageBox.Show(myCanvas.ActualWidth.ToString()); //return 894 Grid testGrid = myCanvas.FindName("CanvasGrid") as Grid; MessageBox.Show("Grid " + testGrid.ActualWidth.ToString()); //return 234 StringReader stringReader = new StringReader(LssAllcChrt); XmlReader xmlReader = XmlReader.Create(stringReader); Canvas myCanvas = newWindow.FindName("GrphCnvs") as Canvas; myCanvas.Children.Clear(); myCanvas.Children.Add((UIElement)XamlReader.Load(xmlReader)); //To test MessageBox.Show(myCanvas.ActualWidth.ToString()); //return 894 but should be much larger the Grid spans all three of my screens Grid testGrid = myCanvas.FindName("CanvasGrid") as Grid; MessageBox.Show("Grid " + testGrid.ActualWidth.ToString()); //return 234 but should be much larger the Grid spans all three of my screens //Run code from WpfUserControl.cs after it loads from button click Grid testGrid = canvas.FindName("CanvasGrid") as Grid; MessageBox.Show("Grid " + testGrid.ActualWidth.ToString()); //return 234 but should be much larger the Grid spans all three of my screens So basically I have no way of telling what my new width and height are.

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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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  • Can you have multiple clipping regions in an HTML Canvas?

    - by emh
    I have code that loads a bunch of images into hidden img elements and then a Javascript loop which places each image onto the canvas. However, I want to clip each image so that it is a circle when placed on the canvas. My loop looks like this: $$('#avatars img').each(function(avatar) { var canvas = $('canvas'); var context = canvas.getContext('2d'); var x = Math.floor(Math.random() * canvas.width); var y = Math.floor(Math.random() * canvas.height); context.beginPath(); context.arc(x+24, y+24, 20, 0, Math.PI * 2, 1); context.clip(); context.strokeStyle = "black"; context.drawImage(document.getElementById(avatar.id), x, y); context.stroke(); }); Problem is, only the first image is drawn (or is visible). If I remove the clipping logic: $$('#avatars img').each(function(avatar) { var canvas = $('canvas'); var context = canvas.getContext('2d'); var x = Math.floor(Math.random() * canvas.width); var y = Math.floor(Math.random() * canvas.height); context.drawImage(document.getElementById(avatar.id), x, y); }); Then all my images are drawn. Is there a way to get each image individually clipped? I tried resetting the clipping area to be the entire canvas between images but that didn't work.

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  • Is there a way to use scala with html5?

    - by Maik Klein
    I want to create a very simple 2d multiplayer browsergame in html5. Something like Scalatron I mainly want to do this to improve my scala skills, the problem is I would have to code the clientside code in javascript and the serverside code in scala. This would result in duplicated code. Another option would be to ignore the html5 part and write it in opengl. But I would still prefer to have a html5 game. I could do this is in javascript, but then it would destroy the whole purpose of learning scala. Is there a way to use scala with html5? Or what would you recommend me to do?

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  • How can a NodeJS server be used from Game Maker HTML5?

    - by Tokyo Dan
    I want to create a client-server game that runs on Game Maker HTML5-NodeJS. The NodeJS server will be an AI server - a bot that acts like a human opponent and plays against the human player at a front-end game client that is coded in GM HTML5. How can a NodeJS server be used from GM HTML5. Are there any examples of such a system? I already got an iOS game that can talk to a remote AI server (coded in Lua) using TCP sockets. Can this be done with Game Maker HTML5 and NodeJS.

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  • Javascript - Canvas image never appears on first function run

    - by Matt
    I'm getting a bit of a weird issue, the image never shows the first time you run the game in your browser, after that you see it every time. If you close your browser and re open it and run the game again, the same issue occurs - you don't see the image the first time you run it. Here's the issue in action, just hit a wall and there's no image the first time on the end game screen. Any help would be appreciated. Regards, Matt function showGameOver() { ctx.clearRect(0, 0, canvas.width, canvas.height); ctx.fillStyle = "black"; ctx.font = "16px sans-serif"; ctx.fillText("Game Over!", ((canvas.width / 2) - (ctx.measureText("Game Over!").width / 2)), 50); ctx.font = "12px sans-serif"; ctx.fillText("Your Score Was: " + score, ((canvas.width / 2) - (ctx.measureText("Your Score Was: " + score).width / 2)), 70); myimage = new Image(); myimage.src = "xcLDp.gif"; var size = [119, 26], //set up size coord = [443, 200]; ctx.font = "12px sans-serif"; ctx.fillText("Restart", ((canvas.width / 2) - (ctx.measureText("Restart").width / 2)), 197); ctx.drawImage( //draw it on canvas myimage, coord[0], coord[1], size[0], size[1] ); $("canvas").click(function(e) { //when click.. if ( testIfOver(this, e, size, coord) ) { startGame(); //reload } }); $("canvas").mousemove(function(e) { //when mouse moving if ( testIfOver(this, e, size, coord) ) { $(this).css("cursor", "pointer"); //change the cursor } else { $(this).css("cursor", "default"); //change it back } }); function testIfOver(ele,ev,size,coord){ if ( ev.pageX > coord[0] + ele.offsetLeft && ev.pageX < coord[0] + size[0] + ele.offsetLeft && ev.pageY > coord[1] + ele.offsetTop && ev.pageY < coord[1] + size[1] + ele.offsetTop ) { return true; } return false; } }

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  • Can anyone list some real examples of 'HTML5' being used in the wild?

    - by betamax
    I am using HTML5 in the same way everyone seems to be using it these days, meaning: HTML5 tags, Canvas / 3D / javascript and CSS3. I am struggling to find examples of sites that are using these technologies practically and that are not just a demo of something cool someone has managed to do using Canvas or CSS3 transforms or shapes. I am looking for sites that have a nice visual look but also take advantage of things like animation, scrolling and offset à la Silverback or the Canvas to create an interactive and I guess 'Flash-looking' site. These are some examples that I have found: Scrolling http://nikebetterworld.com/index http://benthebodyguard.com/ Animation http://www.elladesign.com/contact.html Other http://www.pirateslovedaisies.com/ I am using HTML5 loosely and I hate to be using it. I would be happy if you listed a really visually appealing Javascript-based site but it didn't have the HTML5 doctype.

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  • HTML5 Boilerplate template for ASP.NET with Visual Studio 2010

    - by Harish Ranganathan
    This is the 5th post in the series of HTML5 for ASP.NET Developers  Support for HTML5 in Visual Studio 2010 has been quite good with Visual Studio Service Pack 1 However, HTML5 Boilerplate template has been one of the most popular HTML5 templates out in the internet.  Now, there is one for your favorite ASP.NET Webforms as well as ASP.NET MVC 3 Projects (even for ASP.NET MVC 2).  And its available in the most optimal place, i.e. NuGet. Lets see it in action.  Let us fire up Visual Studio 2010 and create a “File – New Project – ASP.NET Web Application” and leave the default name to create the project.  The default project template creates Site.Master, Default.aspx and the Account (membership) files. When you run the project without any changes, it shows up the default Master Page with the Home and About placeholder pages. Also, just to check the rendering on devices, lets try running the same page in Windows Phone 7 Emulator.  You can download the SDK from here Clearly, it looks bad on the emulator and if we were to publish the application as is, its going to be the same experience when users browse this app. Close the browser and then switch to Visual Studio.   Right click on the project and select “Manage NuGet Packages” The NuGet Package Manager dialog opens up.  Search for HTML5 Boilerplate.  The options for MVC & Web Forms show up.  Click on Install corresponding to the “Add HTML5 Boilerplate to Web Forms” options. It installs the template in a few seconds.   Once installed, you will be able to see a lot of additional Script files and also the all important HTML5Boilerplate.Master file.  This would be the replacement for the default Site.Master.  We need to change the Content Pages (Default.aspx & other pages) to point to this Master Page.  Example <%@ <% Master Language="C#" AutoEventWireup="true" CodeBehind="Html5Boilerplate.Master.cs" Inherits="WebApplication14.SiteMaster" %> would be the setting in the Default.aspx Page. You can do a Find & Replace for Site.Master to HTML5Boilerplate.Master for the whole solution so that it is changed in all the locations. With this, we have our Webforms application ready with HTML5 capabilities.  Needless to say, we need to wire up HTML5 mark up level code, canvas, etc., further to use the actual HTML5 features, but even without that, the page is now HTML5’ed.   One of the advantages of HTML5 (here HTML5 is collectively referred for CSS3, Javascript enhancements etc.,)  is the ability to render the pages better on mobile and hand held devices. So, now when we run the page from Visual Studio, the following is what we get.  Notice the site.icon automatically added.  The page otherwise looks similar to what it was earlier. Now, when we also check this page on the Windows Phone Emulator, here below is what, we get. As you can see, we definitely get a better experience now.  Of course, this is not the only HTML5 feature that we can use.  We need to wire up additional code for using Canvas, SVG and other HTML5 features.  But, definitely, this is a good starting point. You can also install the HTML5boilerplate Template for your ASP.NET MVC 3 and ASP.NET MVC 2 from the NuGet packages and get them ready for HTML5. Cheers !!!

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  • Visual Studio 2010 HTML5

    - by Renso
    Goal: Enabling HTML5 validation and  IntelliSense for Visual Studio 2010. By default it is set to XHTML 1.1. HTML5 support only came included with SP1 of Visual Studio 2010. However since HTML5 is not an official standard as yet and some of the 30 new elements are not suported in all browsers, so only a subset of the entire HTML5 specification is supported; support for both intellisense and validation for HTML5 with SP1. How to: After installing SP1 you have to tell Visual Studio to start using the HTML5 schema. Go to Tools -> Options, and then select Text Editor -> HTML -> Validation. Select HTML5 or XHTML5 as the target schema. So start building or converting older Visual Studio projects to HTML5 and CSS3 web applications.

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  • SmartGWT Canvas width problem

    - by Doug
    I am having problems with showing my entire SmartGWT Canvas on my initial page. I've stripped everything out and am left with an extremely basic EntryPoint to illustrate my issue. When I just create a Canvas and add it to the root panel, I get a horizontal scrollbar in my browser. Can anyone explain why and what I can do to have the Canvas sized to the width of the window? Thanks in advance. public class TestModule implements EntryPoint { protected Canvas view = null; /** * This is the entry point method. */ public void onModuleLoad() { view = new Canvas(); view.setWidth100(); view.setHeight100(); view.setShowEdges( true ); RootPanel.get().add( view ); } }

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  • Firefox throwing a exception with HTML Canvas putImageData

    - by mr.doob
    So I was working on this little javascript experiment and I needed a widget to track the FPS of it. I ported a widget I've been using with Actionscript 3 to Javascript and it seems to be working fine with Chrome/Safari but on Firefox is throwing an exception. This is the experiment: Depth of Field This is the error: [Exception... "An invalid or illegal string was specified" code: "12" nsresult: "0x8053000c (NS_ERROR_DOM_SYNTAX_ERR)" location: "http://mrdoob.com/projects/chromeexperiments/depth_of_field__debug/js/net/hires/debug/Stats.js Line: 105"] The line that is complaning about is this one: graph.putImageData(graphData, 1, 0, 0, 0, 69, 50); Which is a crappy code to "scroll" the bitmap pixels. The idea is that I only draw a few pixels on the left of the bitmap and then on the next frame I copy the whole bitmap and paste it on pixel to the right. This error usually is thrown because you're pasting a bitmap bigger than the source and it's going off the limits, but in theory that shouldn't be the case as I'm defining 69 as the width of the rectangle to paste (being the bitmap 70px wide). And this is full code: var Stats = { baseFps: null, timer: null, timerStart: null, timerLast: null, fps: null, ms: null, container: null, fpsText: null, msText: null, memText: null, memMaxText: null, graph: null, graphData: null, init: function(userfps) { baseFps = userfps; timer = 0; timerStart = new Date() - 0; timerLast = 0; fps = 0; ms = 0; container = document.createElement("div"); container.style.fontFamily = 'Arial'; container.style.fontSize = '10px'; container.style.backgroundColor = '#000033'; container.style.width = '70px'; container.style.paddingTop = '2px'; fpsText = document.createElement("div"); fpsText.style.color = '#ffff00'; fpsText.style.marginLeft = '3px'; fpsText.style.marginBottom = '-3px'; fpsText.innerHTML = "FPS:"; container.appendChild(fpsText); msText = document.createElement("div"); msText.style.color = '#00ff00'; msText.style.marginLeft = '3px'; msText.style.marginBottom = '-3px'; msText.innerHTML = "MS:"; container.appendChild(msText); memText = document.createElement("div"); memText.style.color = '#00ffff'; memText.style.marginLeft = '3px'; memText.style.marginBottom = '-3px'; memText.innerHTML = "MEM:"; container.appendChild(memText); memMaxText = document.createElement("div"); memMaxText.style.color = '#ff0070'; memMaxText.style.marginLeft = '3px'; memMaxText.style.marginBottom = '3px'; memMaxText.innerHTML = "MAX:"; container.appendChild(memMaxText); var canvas = document.createElement("canvas"); canvas.width = 70; canvas.height = 50; container.appendChild(canvas); graph = canvas.getContext("2d"); graph.fillStyle = '#000033'; graph.fillRect(0, 0, canvas.width, canvas.height ); graphData = graph.getImageData(0, 0, canvas.width, canvas.height); setInterval(this.update, 1000/baseFps); return container; }, update: function() { timer = new Date() - timerStart; if ((timer - 1000) > timerLast) { fpsText.innerHTML = "FPS: " + fps + " / " + baseFps; timerLast = timer; graph.putImageData(graphData, 1, 0, 0, 0, 69, 50); graph.fillRect(0,0,1,50); graphData = graph.getImageData(0, 0, 70, 50); var index = ( Math.floor(Math.min(50, (fps / baseFps) * 50)) * 280 /* 70 * 4 */ ); graphData.data[index] = graphData.data[index + 1] = 256; index = ( Math.floor(Math.min(50, 50 - (timer - ms) * .5)) * 280 /* 70 * 4 */ ); graphData.data[index + 1] = 256; graph.putImageData (graphData, 0, 0); fps = 0; } ++fps; msText.innerHTML = "MS: " + (timer - ms); ms = timer; } } Any ideas? Thanks in advance.

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  • How to remove an object from the canvas?

    - by Marius Jonsson
    Hello there, I am making this script that will rotate a needle on a tachometer using canvas. I am a newbie to this canvas. This is my code: function startup() { var canvas = document.getElementById('canvas'); var context = canvas.getContext('2d'); var meter = new Image(); meter.src = 'background.png'; var pin = new Image(); pin.src = 'needle.png'; context.drawImage(meter,0,0); context.translate(275,297); for (var frm = 0; frm < 6000; frm++){ var r=frm/1000; //handle here var i=r*36-27; //angle of rotation from value of r and span var angleInRadians = 3.14159265 * i/180; //converting degree to radian context.rotate(angleInRadians); //rotating by angle context.drawImage(pin,-250,-3); //adjusting pin center at meter center } } Here is the script in action: http://www.kingoslo.com/instruments/ The problem is, as you can see, that the red needle is not removed beetween each for-loop. What I need to do is to clear the canvas for the pin object between each cycle of the loop. How do I do this? Thanks. Kind regards, Marius

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  • How do i tint an image with HTML5 Canvas ?

    - by djdolber
    My question is, what is the best way to tint an image that is drawn using the drawImage method. The target useage for this is advanced 2d particle-effects (game development) where particles change colors over time etc. I am not asking how to tint the whole canvas, only the current image i am about to draw. I have concluded that the globalAlpha parameter affects the current image that is drawn. //works with drawImage() canvas2d.globalAlpha = 0.5; But how do i tint each image with an arbitrary color value ? It would be awesome if there was some kind of globalFillStyle or globalColor or that kind of thing...

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  • How to -accurately- measure size in pixels of text being drawn on a canvas by drawTextOnPath()

    - by Nick
    I'm using drawTextOnPath() to display some text on a Canvas and I need to know the dimensions of the text being drawn. I know this is not feasible for paths composed of multiple segments, curves, etc. but my path is a single segment which is perfectly horizontal. I am using Paint.getTextBounds() to get a Rect with the dimensions of the text I want to draw. I use this rect to draw a bounding box around the text when I draw it at an arbitrary location. Here's some simplified code that reflects what I am currently doing: // to keep this example simple, always at origin (0,0) public drawBoundedText(Canvas canvas, String text, Paint paint) { Rect textDims = new Rect(); paint.getTextBounds(text,0, text.length(), textDims); float hOffset = 0; float vOffset = paint.getFontMetrics().descent; // vertically centers text float startX = textDims.left; / 0 float startY = textDims.bottom; float endX = textDims.right; float endY = textDims.bottom; path.moveTo(startX, startY); path.lineTo(endX, endY); path.close(); // draw the text canvas.drawTextOnPath(text, path, 0, vOffset, paint); // draw bounding box canvas.drawRect(textDims, paint); } The results are -close- but not perfect. If I replace the second to last line with: canvas.drawText(text, startX, startY - vOffset, paint); Then it works perfectly. Usually there is a gap of 1-3 pixels on the right and bottom edges. The error seems to vary with font size as well. Any ideas? It's possible I'm doing everything right and the problem is with drawTextOnPath(); the text quality very visibly degrades when drawing along paths, even if the path is horizontal, likely because of the interpolation algorithm or whatever its using behind the scenes. I wouldnt be surprised to find out that the size jitter is also coming from there.

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  • Download Canvas Image Png Chome/Safari

    - by user2639176
    Works in Firefox, and won't work in Safari, or Chrome. function loadimage() { var canvas = document.getElementById("canvas"); if (window.XMLHttpRequest) {// code for IE7+, Firefox, Chrome, Opera, Safari xmlhttp=new XMLHttpRequest(); xmlhttp2=new XMLHttpRequest(); } else {// code for IE6, IE5 xmlhttp=new ActiveXObject("Microsoft.XMLHTTP"); xmlhttp2=new ActiveXObject("Microsoft.XMLHTTP"); } xmlhttp.onreadystatechange=function() { if (xmlhttp.readyState==4 && xmlhttp.status==200) { rasterizeHTML.drawHTML(xmlhttp.responseText, canvas); var t=setTimeout(function(){copy()},3000) } } xmlhttp.open("GET","/sm/<?=$sm[0];?>",true); xmlhttp.send(); } function copy() { var canvas = document.getElementById("canvas"); var img = canvas.toDataURL("image/png"); document.getElementById('dl').href = img; document.getElementById('dl').innerHTML = "Download"; } Now I didn't write this, so I don't know too much javascript. But the script works in Firefox. In Chrome, getting: Uncaught Security Error: An attempt was made to break through the security policy of the user-agent. For toDataURL("image/png")

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  • How to update off screen bitmap in a surfaceview thread

    - by DKDiveDude
    I have a Surfaceview thread and an off canvas texture bitmap that is being generated (changed), first row (line), every frame and then copied one position (line) down on regular surfaceview bitmap to make a scrolling effect, and I then continue to draw other things on top of that. Well that is what I really want, however I can't get it to work even though I am creating a separate canvas for off screen bitmap. It is just not scrolling at all. I other words I have a memory bitmap, same size as Surfaceview canvas, which I need to scroll (shift) down one line every frame, and then replace top line with new random texture, and then draw that on regular Surfaceview canvas. Here is what I thought would work; My surfaceChanged where I specify bitmap and canvasses and start thread: @Override public void surfaceCreated(SurfaceHolder holder) { intSurfaceWidth = mSurfaceView.getWidth(); intSurfaceHeight = mSurfaceView.getHeight(); memBitmap = Bitmap.createBitmap(intSurfaceWidth, intSurfaceHeight, Bitmap.Config.ARGB_8888); memCanvas = new Canvas(memCanvas); myThread = new MyThread(holder, this); myThread.setRunning(true); blnPause = false; myThread.start(); } My thread, only showing essential middle running part: @Override public void run() { while (running) { c = null; try { // Lock canvas for drawing c = myHolder.lockCanvas(null); synchronized (mSurfaceHolder) { // First draw off screen bitmap to off screen canvas one line down memCanvas.drawBitmap(memBitmap, 0, 1, null); // Create random one line(row) texture bitmap memTexture = Bitmap.createBitmap(imgTexture, 0, rnd.nextInt(intTextureImageHeight), intSurfaceWidth, 1); // Now add this texture bitmap to top of off screen canvas and hopefully bitmap memCanvas.drawBitmap(textureBitmap, intSurfaceWidth, 0, null); // Draw above updated off screen bitmap to regular canvas, at least I thought it would update (save changes) shifting down and add the texture line to off screen bitmap the off screen canvas was pointing to. c.drawBitmap(memBitmap, 0, 0, null); // Other drawing to canvas comes here } finally { // do this in a finally so that if an exception is thrown // during the above, we don't leave the Surface in an // inconsistent state if (c != null) { myHolder.unlockCanvasAndPost(c); } } } } For my game Tunnel Run. Right now I have a working solution where I instead have an array of bitmaps, size of surface height, that I populate with my random texture and then shift down in a loop for each frame. I get 50 frames per second, but I think I can do better by instead scrolling bitmap.

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