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Preview thumbnails of uploaded image attachments before posting on supporting browsers. 

Tested working so far:
* Firefox 3.6 and 4.0 (FileReader -> data URL)
* Chrome 8 (createObjectURL; FileReader also works)

Tested with limited support:
* Safari 5.0.3 (no preview, but we can show type and size)

Tested and known not to support FileAPI, keeps current behavior:
* Opera 11 beta
This commit is contained in:
Brion Vibber 2010-11-24 12:20:25 -08:00
parent b6e5b1d294
commit d075fac7b8
1 changed files with 94 additions and 0 deletions
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94
js/util.js
View File

@ -457,9 +457,103 @@ var SN = { // StatusNet
return false;
});
if (typeof this.files == "object") {
// Some newer browsers will let us fetch the files for preview.
for (var i = 0; i < this.files.length; i++) {
SN.U.PreviewAttach(this.files[i]);
}
}
});
},
/**
* For browsers with FileAPI support: make a thumbnail if possible,
* and append it into the attachment display widget.
*
* Known good:
* - Firefox 3.6.6, 4.0b7
* - Chrome 8.0.552.210
*
* Known ok metadata, can't get contents:
* - Safari 5.0.2
*
* Known fail:
* - Opera 10.63, 11 beta (no input.files interface)
*
* @param {File} file
*
* @todo use configured thumbnail size
* @todo detect pixel size?
* @todo should we render a thumbnail to a canvas and then use the smaller image?
*/
PreviewAttach: function(file) {
var tooltip = file.type + ' ' + Math.round(file.size / 1024) + 'KB';
var preview = true;
var blobAsDataURL;
if (typeof window.createObjectURL != "undefined") {
/**
* createObjectURL lets us reference the file directly from an <img>
* This produces a compact URL with an opaque reference to the file,
* which we can reference immediately.
*
* - Firefox 3.6.6: no
* - Firefox 4.0b7: no
* - Safari 5.0.2: no
* - Chrome 8.0.552.210: works!
*/
blobAsDataURL = function(blob, callback) {
callback(window.createObjectURL(blob));
}
} else if (typeof window.FileReader != "undefined") {
/**
* FileAPI's FileReader can build a data URL from a blob's contents,
* but it must read the file and build it asynchronously. This means
* we'll be passing a giant data URL around, which may be inefficient.
*
* - Firefox 3.6.6: works!
* - Firefox 4.0b7: works!
* - Safari 5.0.2: no
* - Chrome 8.0.552.210: works!
*/
blobAsDataURL = function(blob, callback) {
var reader = new FileReader();
reader.onload = function(event) {
callback(reader.result);
}
reader.readAsDataURL(blob);
}
} else {
preview = false;
}
var imageTypes = ['image/png', 'image/jpeg', 'image/gif', 'image/svg+xml'];
if ($.inArray(file.type, imageTypes) == -1) {
// We probably don't know how to show the file.
preview = false;
}
var maxSize = 8 * 1024 * 1024;
if (file.size > maxSize) {
// Don't kill the browser trying to load some giant image.
preview = false;
}
if (preview) {
blobAsDataURL(file, function(url) {
var img = $('<img>')
.attr('title', tooltip)
.attr('alt', tooltip)
.attr('src', url)
.attr('style', 'height: 120px');
$('#'+SN.C.S.NoticeDataAttachSelected).append(img);
});
} else {
var img = $('<div></div>').text(tooltip);
$('#'+SN.C.S.NoticeDataAttachSelected).append(img);
}
},
NoticeLocationAttach: function() {
var NLat = $('#'+SN.C.S.NoticeLat).val();
var NLon = $('#'+SN.C.S.NoticeLon).val();