Re: [whatwg] createImageData - new ImageData() ?
On Sun, 10 Feb 2008 23:25:51 -, Ian Hickson [EMAIL PROTECTED] wrote: That would mean that passing ImageData around between two canvas elements doesn't always work as expected. I think that's highly undesirable. Is there any implementation where we know this will the case? Not today, but why preclude it? Implementations could get higher quality renderings on canvases that get resized dynamically, by using a bigger backing store. What's wrong with what we have now? It's very easy to write code which assumes that size of imageData is the same as size given in canvas width height (I know, because I did it :) Since the ratio is system/browser-dependent and 200dpi screens aren't popular yet, such bug may be easily overlooked/ignored and get widely deployed. The difference in sizes isn't intuitive. For example if browser doubled number of pixels in ImageData only when user used zoom, I think authors would rather think that browser's zoom is buggy. I think that by default getImageData should return data with same size as specified in width/height attributes of canvas. There might be another method (getImageScreenData?) or method argument that returns all pixels of canvas. ImageData can be made portable between canvases by adding aspect ratio field or additional width/height fields given in CSS pixels. -- regards, Kornel Lesiński
Re: [whatwg] createImageData - new ImageData() ?
On Sun, 3 Feb 2008, Anne van Kesteren wrote: Why not give the object a constructor? I think that's cleaner. Also, Opera already supports that :-) The relationship between the height and width arguments and the height and width of the ImageData structure returned can vary on a per-canvas basis. -- Ian Hickson U+1047E)\._.,--,'``.fL http://ln.hixie.ch/ U+263A/, _.. \ _\ ;`._ ,. Things that are impossible just take longer. `._.-(,_..'--(,_..'`-.;.'
Re: [whatwg] createImageData - new ImageData() ?
On Sun, 10 Feb 2008 10:21:34 +0100, Ian Hickson [EMAIL PROTECTED] wrote: On Sun, 3 Feb 2008, Anne van Kesteren wrote: Why not give the object a constructor? I think that's cleaner. Also, Opera already supports that :-) The relationship between the height and width arguments and the height and width of the ImageData structure returned can vary on a per-canvas basis. That would mean that passing ImageData around between two canvas elements doesn't always work as expected. I think that's highly undesirable. Is there any implementation where we know this will the case? -- Anne van Kesteren http://annevankesteren.nl/ http://www.opera.com/
Re: [whatwg] createImageData - new ImageData() ?
On Feb 10, 2008 11:14 PM, Anne van Kesteren [EMAIL PROTECTED] wrote: That would mean that passing ImageData around between two canvas elements doesn't always work as expected. I think that's highly undesirable. Is there any implementation where we know this will the case? Not yet, but in Gecko when we get around to implementing variable-resolution canvas backing stores, I expect it would happen because different documents --- even different documents that can reference each other --- can be zoomed different amounts, which affects the device-pixels-per-CSS-pixel ratio we use internally. It's actually worse than that, because we respond to dynamic DPI changes (due to zooming or changes in preferences; I'm not sure if we actually support detection of hardware DPI changes, e.g. due to screen mode switching, but we easily could). So we might want to dynamically rescale the canvas backing store. Rob -- He was pierced for our transgressions, he was crushed for our iniquities; the punishment that brought us peace was upon him, and by his wounds we are healed. We all, like sheep, have gone astray, each of us has turned to his own way; and the LORD has laid on him the iniquity of us all. [Isaiah 53:5-6]
Re: [whatwg] createImageData - new ImageData() ?
On Sun, 10 Feb 2008, Anne van Kesteren wrote: On Sun, 10 Feb 2008 10:21:34 +0100, Ian Hickson [EMAIL PROTECTED] wrote: On Sun, 3 Feb 2008, Anne van Kesteren wrote: Why not give the object a constructor? I think that's cleaner. Also, Opera already supports that :-) The relationship between the height and width arguments and the height and width of the ImageData structure returned can vary on a per-canvas basis. That would mean that passing ImageData around between two canvas elements doesn't always work as expected. I think that's highly undesirable. Is there any implementation where we know this will the case? Not today, but why preclude it? Implementations could get higher quality renderings on canvases that get resized dynamically, by using a bigger backing store. What's wrong with what we have now? -- Ian Hickson U+1047E)\._.,--,'``.fL http://ln.hixie.ch/ U+263A/, _.. \ _\ ;`._ ,. Things that are impossible just take longer. `._.-(,_..'--(,_..'`-.;.'
[whatwg] createImageData - new ImageData() ?
Why not give the object a constructor? I think that's cleaner. Also, Opera already supports that :-) -- Anne van Kesteren http://annevankesteren.nl/ http://www.opera.com/
Re: [whatwg] createImageData - new ImageData() ?
On Feb 3, 2008, at 2:38 AM, Anne van Kesteren wrote: Why not give the object a constructor? I think that's cleaner. Also, Opera already supports that :-) The biggest problem is that you would have to define the behaviour in a fairly counterintuitive way new ImageData(400, 400) would not necessarily result in an ImageData object with width=400, height=400 as a system with a non-1:1 css to device pixel ratio. The moment people start using getImageData() as storage mechanism (which they will if browsers do not fix their data: image origin stuff) you'll have a problem with this if the application is accessed through different devices that have different ratios. I suspect though that given that Firefox has a 1:1 ratio sites will simply rely on that... Part of my commentary was on a misunderstanding of the spec sorry :( That said, what do you mean by using getImageData as a storage mechanism? --Oliver -- Anne van Kesteren http://annevankesteren.nl/ http://www.opera.com/
Re: [whatwg] createImageData - new ImageData() ?
On Sun, 03 Feb 2008 12:20:54 +0100, Oliver Hunt [EMAIL PROTECTED] wrote: On Feb 3, 2008, at 2:38 AM, Anne van Kesteren wrote: Why not give the object a constructor? I think that's cleaner. Also, Opera already supports that :-) The biggest problem is that you would have to define the behaviour in a fairly counterintuitive way new ImageData(400, 400) would not necessarily result in an ImageData object with width=400, height=400 as a system with a non-1:1 css to device pixel ratio. How is this a non-issue for createImageData()? The moment people start using getImageData() as storage mechanism (which they will if browsers do not fix their data: image origin stuff) you'll have a problem with this if the application is accessed through different devices that have different ratios. I suspect though that given that Firefox has a 1:1 ratio sites will simply rely on that... Part of my commentary was on a misunderstanding of the spec sorry :( That said, what do you mean by using getImageData as a storage mechanism? If you have some kind of painting application and to store the result of the painting so that the user can edit it in another session every now and then you do getImageData() on the whole canvas and export the data to some database through XMLHttpRequest so when the visitor comes back he doesn't have to start all over again. -- Anne van Kesteren http://annevankesteren.nl/ http://www.opera.com/
