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Xjpc image mime type options #1

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Xjpc image mime type options #1

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ded8cb5
Update README.md
manukautech Dec 19, 2018
a237375
Update diff-cam-engine.js
manukautech Dec 19, 2018
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4 changes: 3 additions & 1 deletion README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -6,7 +6,7 @@ Core engine for building motion detection web apps.

`diff-cam-engine.js` provides a `DiffCamEngine` object that accesses the webcam, captures images from it, and evaluates motion.

You'll want to use the `adapter.js` shim, which is available here: https://github.com/webrtc/adapter. Add it before `diff-cam-engine.js`.
If you have browser compatibility issues, you can try the `adapter.js` shim, which is available here: https://github.com/webrtc/adapter. Add it before `diff-cam-engine.js`.

With that in place, call `DiffCamEngine.init()` to initialize. This will set things up and ask the user for permission to access the webcam.

Expand Down Expand Up @@ -48,6 +48,8 @@ The following variables can be passed into `init()`:
| diffHeight | 48 | Height of (usually downsized) images used for diffing and showing motion |
| pixelDiffThreshold | 32 | Minimum difference in a pixel to be considered changed |
| scoreThreshold | 16 | Minimum number of changed pixels for an image to be considered as having motion |
| imageMimeType | "image/jpeg" | mime type string e.g. "image/jpeg", "image/png" |
| jpegQuality | 0.7 | "image/jpeg" quality value between 0 and 1 |
| includeMotionBox | false | Flag to calculate and display (on motionCanvas) the bounding box of motion |
| includeMotionPixels | false | Flag to include data indicating all the changed pixels |

Expand Down
42 changes: 26 additions & 16 deletions diff-cam-engine.js
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Original file line number Diff line number Diff line change
@@ -1,12 +1,14 @@
var DiffCamEngine = (function() {
var stream; // stream obtained from webcam
var video; // shows stream
var captureCanvas; // internal canvas for capturing full images from video
var captureContext; // context for capture canvas
var diffCanvas; // internal canvas for diffing downscaled captures
var diffContext; // context for diff canvas
var motionCanvas; // receives processed diff images
var motionContext; // context for motion canvas
var stream; // stream obtained from webcam
var video; // shows stream
var captureCanvas; // internal canvas for capturing full images from video
var captureContext; // context for capture canvas
var diffCanvas; // internal canvas for diffing downscaled captures
var diffContext; // context for diff canvas
var motionCanvas; // receives processed diff images
var motionContext; // context for motion canvas
var imageMimeType; // string e.g. "image/jpeg", "image/png"
var jpegQuality; // imageMimeType:"image/jpeg" quality value between 0 and 1

var initSuccessCallback; // called when init succeeds
var initErrorCallback; // called when init fails
Expand All @@ -15,13 +17,13 @@ var DiffCamEngine = (function() {

var captureInterval; // interval for continuous captures
var captureIntervalTime; // time between captures, in ms
var captureWidth; // full captured image width
var captureHeight; // full captured image height
var diffWidth; // downscaled width for diff/motion
var diffHeight; // downscaled height for diff/motion
var isReadyToDiff; // has a previous capture been made to diff against?
var captureWidth; // full captured image width
var captureHeight; // full captured image height
var diffWidth; // downscaled width for diff/motion
var diffHeight; // downscaled height for diff/motion
var isReadyToDiff; // has a previous capture been made to diff against?
var pixelDiffThreshold; // min for a pixel to be considered significant
var scoreThreshold; // min for an image to be considered significant
var scoreThreshold; // min for an image to be considered significant
var includeMotionBox; // flag to calculate and draw motion bounding box
var includeMotionPixels; // flag to create object denoting pixels with motion

Expand All @@ -43,6 +45,8 @@ var DiffCamEngine = (function() {
scoreThreshold = options.scoreThreshold || 16;
includeMotionBox = options.includeMotionBox || false;
includeMotionPixels = options.includeMotionPixels || false;
imageMimeType = options.imageMimeType || "image/jpeg";
jpegQuality = options.jpegQuality || 0.7;

// callbacks
initSuccessCallback = options.initSuccessCallback || function() {};
Expand Down Expand Up @@ -153,7 +157,7 @@ var DiffCamEngine = (function() {
return getCaptureUrl(this.imageData);
},
checkMotionPixel: function(x, y) {
return checkMotionPixel(this.motionPixels, x, y)
return checkMotionPixel(this.motionPixels, x, y);
}
});
}
Expand Down Expand Up @@ -232,7 +236,13 @@ var DiffCamEngine = (function() {
function getCaptureUrl(captureImageData) {
// may as well borrow captureCanvas
captureContext.putImageData(captureImageData, 0, 0);
return captureCanvas.toDataURL();
//image mime type
//ref: https://developer.mozilla.org/en-US/docs/Web/API/HTMLCanvasElement/toDataURL
if (imageMimeType == "image/jpeg") {
return captureCanvas.toDataURL("image/jpeg", jpegQuality);
} else {
return captureCanvas.toDataURL(imageMimeType);
}
}

function checkMotionPixel(motionPixels, x, y) {
Expand Down