Here is the
updated code:
function drawImg(){
var canvas = document.getElementById(???myCanvas??™);
var context = canvas.getContext(???2d??™);
var img = new Image();
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133
img.src = ???images/beach.jpg??™;
img.onload = function() {
context.drawImage( img, 151, 63, 79, 131, 10, 10, 79, 131 );
}
}
Figure 6-5 shows the result.
Figure 6-5: Painting a portion of an image
You can also use a data: URI encoded image (see Chapter 10 for more details on data: URI encoding) to
eliminate the need for an external image file altogether for canvas painting. For example, start with an
online image encoder, such as the one available at www.scalora.org/projects/uriencoder . Using
this tool, you encode the image, as shown in Figure 6-6 .
Chapter 6: Advanced Programming Topics: Canvas and Video
134
Figure 6-6: Encoding an image
The outputted encoded string can then be integrated into the script code as the image object??™s source
(much of the encoded text for this example has been removed for space reasons):
function drawImg(){
var img_src = ???data:image/jpeg;base64,??™ +
???/9j/4AAQSkZJRgABAgAAZABkAAD/7AARRHVja3kAAQAEAAAAMAAA/+4ADkFkb2JlAGTAAAAAAf/bAIQA??™ +
???CQYGBgcGCQcHCQ0IBwgNDwsJCQsPEQ4ODw4OERENDg4ODg0RERQUFhQUERoaHBwaGiYmJiYmKysrKysr??™ +
???KysrKwEJCAgJCgkMCgoMDwwODA8TDg4ODhMVDg4PDg4VGhMRERERExoXGhYWFhoXHR0aGh0dJCQjJCQr??™ +
???KysrKysrKysr/8AAEQgA4AEsAwEiAAIRAQMRAf/EAJ8AAAEFAQEBAAAAAAAAAAAAAAIBAwQFBgAHCAEA??™ +
???AwEBAQAAAAAAAAAAAAAAAAECAwQFEAABAwIEAwUFBQcEAQUAAAABAAIDEQQhMRIFQVETYXGBIgaRoTIj??™ +
???FLFCUnIzwdFiQyQ0B+GCkhWy0lODNRcRAAICAQMCBAUDBAMAAAAAAAABEQIhMRIDQVFhcYEikaGxEwTB??™ +
???MkLw4VIj0WKC/9oADAMBAAIRAxEAPwDyO2t5TdRAvJbqHFaWRkETzCMzia8VSMEocxw+HVg5WgIke0vq??™ +
???ZKLmtk6Ke0tYmgRNAypglK6MUiaOQXEKCgSkSlImIRWcA+U3uVaFaQj5be5AMKi6iVcgQKSiJIgBKLkq??™ +
???5ACLkq5ACLkq5ACJEq5ACJKJVyABXFKkQAiQhKUiAEKSiIpKIAAhCQjSEIAAoSEZQlAgaLqJaJQEDGbg??™ +
???VhcOYTO0A9N/IHBPXf6Du5DtbKQuPBxr7kpyOMD9x+i/8pWQ/m+P7VsLr+3k/KVj/wCZ4p9GLsT/APp9??™ +
???OmIIzR8p0jsHErPNY1jQxowbgpW5TOudxkfm2LyN7zi5R8u5IlvIJAPYhPvRHNDkfsTEXnpO1tXXcu4X??™ +
???rOpY7TC67ljOT3g6YYj+Z5CsLL1B6lvPUcTTdyPmmma18IPyg2vnb08tLW1Xendsu7v08+K2idI7cdwg??™ +
???hl0jAQwMMz9R4CrhmrqT07centnvNyaz6neJ2O1Ob8NvHJ+oWfiIriV2cfHfZV1lJe+zX0+BwcvLx77q??™ +
???0Ws/9dE/r4Z1M5u8zX7zaQwnRbwuj6IpgOrKZtQH+9Qt7AG87g0ClLmYAf8AyOVptdp1vU9iJcI7SOG4??™ +
???m1cGQRNld/4qpguDcbg64lo8zPkmdq/FR0gPtWPIpTnG6+PRf3N+PDUZ28cv/wBP+wF8a3cnGhDa9rQG??™ +
???n7FHfknnwyCBk7h5JXODXE4ktpqw8V13Z3VqY23MToTK3qMDsKtOFfaFg02248fidCaSSnw+AwE5FHJK??™ +
???8MYKuOPIADMk8AOKft7a7EzIxZOnlkAfHG5j6uacjpbQlpVlJuh28fTRWVtb3rD/AFB6OsUFCI/nl3eV??™ +
???VeNRNnCXgTbkcxVbm/H5kaBn09jNcwQNuomPZFLdPJDWudiGRsqCa0zPsUKW7nlFCQxnFjAGtFewLZv9??™ +
???Y3EOxWt4yxtRNPM+Jw0DSTG0fM0tpj5lRyerdzeySLo2jYpfijFtHT3hbcleNKqXI9JhV7mPFfls7N8S??™ +
???w4l27YfQoySSTmTxS0XONXF1AKmtAKDwCTCq5TqDM0jm6SQRliATQDTnRABRKEqG2wwhF3euK5AAkJT7??™ +
???lyRACJOK4lCD5jjkgQYxNEkhp5R4pNWkVGaCpOJzKcBIuCRKkOaBirqmlOGdF1SuwSGenAp+U/IPco4K??™ +
???duHhls9xya0krZHP0Kbc7k9Nlow4yCslPw8vFdZQgDLioUTnTSumdm817hwVrbUHgsnlnVVbak6BoACl??™ +
Chapter 6: Advanced Programming Topics: Canvas and Video
135
???tywUWM44J8O9ipCZz60VLvc/Tt3mvBWssoaM1nN3c65kZA3OV7WD/caIYkZ6/wBpvdvbFJcN8l03qxyD??™ +
???I6vNpPaFDIBHby5r1q9261vLF1jcN1RaQ0c2loo1ze0LzDddtn2y8fazCtMWP4PacnBJCsoK84Yc8ihJ??™ +
???4HNE7t45psk6gDmEyGeibFul7snoqO7tdIDhcyOLhUdR0sUMOHZ5lVbDvO4Xd/fyXtw+461lOJNZqMhS??™ +
???jchSvBO31yGf4422AHGa5fXuY6R32kLP7XeiyuxM8F0T2vilAz0SN0mnaM12X5HW3Cpaqq1b7ZOKnErU??™ +
???57bU7O9kn1wzf7fBt9pDPudwDNdbna6YoWsLi2GFjWSup/E6lexQrR8M/pq93G7gbd3AdNBFduYGOdEG??™ +
???lzHUAwAJIw7lQWPq7dba4MshbdQuPmhkGAYRpc2NwoWVbhhgrrbmnfrXc4LS5kc6b6ZvSdGyJsMQkNWM??™ +
???axxaaCuQFfFaU5aXxTWLe3u9ZMr8N+NbrvE19yelU4jwKpkcMVtbXWirLG0bcVPGaSWRsbSPzmvc1X+3??™ +
???emYtw2fZru9A0NdNeX9w8+YxF3Uax1eD8yqrcd22yz3C92qe1N3tzGQWvy39N4NsDVzTjm5xVZuXqndL??™ +
???xs9tFK6322UgMtGkUaxrQxrNVK0o3FZ7+Ljb3e6Ft2r/ACX6YNdnNyJbfZL3bn/jZaefuZ6BZ+p9svLG??™ +
???43Nhi+rtnTR2keHUERLWMcWA6tJzPYsp61sWTGHeLZ8cwlAivei7W1k1ARjn5gciskCpdhul/t7nus5j??™ +
???D1BpkAALXDhVrgRUcCov+WuSuy9YT6rv3gvj/D+1ffx2yuj0jtJO3d4isLHbqaZbQPM7eIllDZHA9orp??™ +
???8FUpQ/W8ulJLnnU5+bqnEnE41SEAU0mtQCcKUPJc17bnPTReSwdVK7axq8tvxeWcVyTilUFnLly5AHJC??™ +
???lJQlAjkhPtSoCUwEJQB2LkvFNu8rimhMPVq8EtUDCKdiJApCqhOaXguSKOCVCi4I6h0P/9k=??™;
var canvas = document.
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