{"id":18,"date":"2012-05-07T22:04:07","date_gmt":"2012-05-07T22:04:07","guid":{"rendered":"http:\/\/beta.robertprice.co.uk\/robblog\/2012\/05\/scaling_an_image_in_an_html5_canvas-shtml\/"},"modified":"2012-05-07T22:04:07","modified_gmt":"2012-05-07T22:04:07","slug":"scaling_an_image_in_an_html5_canvas-shtml","status":"publish","type":"post","link":"https:\/\/www.robertprice.co.uk\/robblog\/scaling_an_image_in_an_html5_canvas-shtml\/","title":{"rendered":"Scaling An Image In An HTML5 Canvas"},"content":{"rendered":"<p>\nAs part of my Draw Something Solver, I&#8217;ve been working with HTML 5 Canvas objects quite a bit. As I want my application to work on all iPhones, I need to support both regular and retina displays. As I need to detect the letters on the image, I really need the images to be of the same size, however a regular image is 320&#215;480, whereas a retina image is 640&#215;960.\n<\/p>\n<p>\nThe eagle eyed amongst you will see that this is a factor of 2 difference between the two.\n<\/p>\n<p>\nThe Canvas Context object provides a <var>scale()<\/var> method, that you pass in x and y scaling factors into.\n<\/p>\n<p>\nSo if I have a Canvas object called <var>screenshotCanvas<\/var>, and an Image object called <var>screenshotImage<\/var> I want to scale down by half, I can use the following JavaScript code.\n<\/p>\n<pre class=\"lang:js decode:true \" >screenshotCanvasContext = screenshotCanvas.getContext('2d');\nscreenshotCanvasContext.scale(0.5, 0.5);\nscreenshotCanvasContext.drawImage(screenshotImage,\n                                  0,\n                                  0,\n                                  screenshotImage.width,\n                                  screenshotImage.height);\n<\/pre>\n<p>\nIf I want to double the image in size, I just change the scale factor to 2.\n<\/p>\n<pre class=\"lang:js decode:true \" >screenshotCanvasContext = screenshotCanvas.getContext('2d');\nscreenshotCanvasContext.scale(2, 2);\nscreenshotCanvasContext.drawImage(screenshotImage,\n                                  0,\n                                  0,\n                                  screenshotImage.width,\n                                  screenshotImage.height);\n<\/pre>\n","protected":false},"excerpt":{"rendered":"<p>As part of my Draw Something Solver, I&#8217;ve been working with HTML 5 Canvas objects quite a bit. As I want my application to work on all iPhones, I need to support both regular and retina displays. As I need to detect the letters on the image, I really need the images to be of &hellip; <a href=\"https:\/\/www.robertprice.co.uk\/robblog\/scaling_an_image_in_an_html5_canvas-shtml\/\" class=\"more-link\">Continue reading<span class=\"screen-reader-text\"> &#8220;Scaling An Image In An HTML5 Canvas&#8221;<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"inline_featured_image":false,"footnotes":""},"categories":[2],"tags":[24,31],"class_list":["post-18","post","type-post","status-publish","format-standard","hentry","category-dev","tag-html5","tag-javascript"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v27.7 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>Scaling An Image In An HTML5 Canvas - Robert Price<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.robertprice.co.uk\/robblog\/scaling_an_image_in_an_html5_canvas-shtml\/\" \/>\n<meta property=\"og:locale\" content=\"en_GB\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Scaling An Image In An HTML5 Canvas - Robert Price\" \/>\n<meta property=\"og:description\" content=\"As part of my Draw Something Solver, I&#8217;ve been working with HTML 5 Canvas objects quite a bit. 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