提高图像拖动速度

Question

背景：

1。用户单击遮罩，然后将自己的图像上传到蒙版上。...

2。上传图片后，用户可以拖动上传的图片。...

要求：

我感觉拖动非常慢，我真的想使其变得超快和流畅。...

Codepen：https://codepen.io/kidsdial/pen/QPoRyM

提琴：https://jsfiddle.net/kidsdial1/g58nrf7e/

以下是代码段：

var target;
const imageUrl = "https://i.imgur.com/RzEm1WK.png";

let jsonData = {
    "layers": [{
        "x": 0,
        "height": 612,
        "layers": [{
                "x": 160,
                "src": "ax0HVTs.png",
                "y": 291,
                "height": 296,
                "width": 429,
                "name": "mask_1"
            },
            {
                "x": 25,
                "src": "hEM2kEP.png",
                "height": 324,
                "width": 471,
                "y": 22,
                "name": "mask_2"
            }
        ],
        "y": 0,
        "width": 612
    }]
};

const containerElement = $('#container');
const fileUp = $('#fileup');

$(function() {

    // Upload image onclick mask image 

    containerElement.click(function(e) {
        var res = e.target;
        target = res.id;
        console.log(target);
        if (e.target.getContext) {
            // click only inside Non Transparent part
            var pixel = e.target.getContext('2d').getImageData(e.offsetX, e.offsetY, 1, 1).data;
            if (pixel[3] === 255) {
                setTimeout(() => {
                    $('#fileup').click();
                }, 20);
            }
        }
    });

    // Fetch mask images from json file - IGNORE this code

    function getAllSrc(layers) {
        let arr = [];
        layers.forEach(layer => {
            if (layer.src) {
                arr.push({
                    src: layer.src,
                    x: layer.x,
                    y: layer.y,
                    height: layer.height,
                    width: layer.width,
                    name: layer.name
                });
            } else if (layer.layers) {
                let newArr = getAllSrc(layer.layers);
                if (newArr.length > 0) {
                    newArr.forEach(({
                        src,
                        x,
                        y,
                        height,
                        width,
                        name
                    }) => {
                        arr.push({
                            src,
                            x: (layer.x + x),
                            y: (layer.y + y),
                            height,
                            width,
                            name: (name)
                        });
                    });
                }
            }
        });
        return arr;
    }

    function json(data)

    {
        var width = 0;
        var height = 0;

        let arr = getAllSrc(data.layers);

        let layer1 = data.layers;
        width = layer1[0].width;
        height = layer1[0].height;
        let counter = 0;
        let table = [];

        // container dimensions
        containerElement.css('width', width + "px").css('height', height + "px").addClass('temp');
        //end

        for (let {
                src,
                x,
                y,
                name
            } of arr) {

            //Get Height and width of mask image [ edit button ]
            var ImagePosition = arr;
            //code end

            var mask = $(".container").mask({
                imageUrl: imageUrl,

                // Fetch Mask images
                maskImageUrl: 'https://i.imgur.com/' + src,
                // end

                onMaskImageCreate: function(img) {
                    // Mask image positions
                    img.css({
                        "position": "absolute",
                        "left": x + "px",
                        "top": y + "px"
                    });
                    // end

                },
                id: counter
            });
            table.push(mask);
            fileup.onchange = function() {

                let mask2 = table[target];
                const newImageLoadedId = mask2.loadImage(URL.createObjectURL(fileup.files[0]));
                document.getElementById('fileup').value = "";                          
            };
            counter++;
        }
    }
    json(jsonData);
}); // end of function

// Image code

(function($) {
    var JQmasks = [];
    $.fn.mask = function(options) {
        // This is the easiest way to have default options.
        var settings = $.extend({
            // These are the defaults.
            maskImageUrl: undefined,
            imageUrl: undefined,
            scale: 1,
            id: new Date().getUTCMilliseconds().toString(),
            x: 0, // image start position
            y: 0, // image start position
            onMaskImageCreate: function(div) {},
        }, options);


        var container = $(this);

        let prevX = 0,
            prevY = 0,
            draggable = false,
            img,
            canvas,
            context,
            image,
            timeout,
            initImage = false,
            startX = settings.x,
            startY = settings.y,
            div;

        container.mousePosition = function(event) {
            return {
                x: event.pageX || event.offsetX,
                y: event.pageY || event.offsetY
            };
        }

        container.selected = function(ev) {
            var pos = container.mousePosition(ev);
            var item = $(".masked-img canvas").filter(function() {
                var offset = $(this).offset()
                var x = pos.x - offset.left;
                var y = pos.y - offset.top;
                var d = this.getContext('2d').getImageData(x, y, 1, 1).data;
                return d[0] > 0
            });

            JQmasks.forEach(function(el) {
                var id = item.length > 0 ? $(item).attr("id") : "";
                if (el.id == id)
                    el.item.enable();
                else el.item.disable();
            });
        };

        container.enable = function() {
            draggable = true;
            $(canvas).attr("active", "true");
            div.css({
                "z-index": 2
            });
        }

        container.disable = function() {
            draggable = false;
            $(canvas).attr("active", "false");
            div.css({
                "z-index": 1
            });
        }

        container.getImagePosition = function() {
            return {
                x: settings.x,
                y: settings.y,
                scale: settings.scale
            };
        };

        // Drag uploaded image

        container.onDragStart = function(evt) {
            if (evt.target.getContext) {
                var pixel = evt.target.getContext('2d').getImageData(evt.offsetX, evt.offsetY, 1, 1).data;

                $(canvas).attr("active", "true");
                container.selected(evt);
                prevX = evt.clientX;
                prevY = evt.clientY;
                var img = new Image();
                evt.originalEvent.dataTransfer.setDragImage(img, 10, 10);
                evt.originalEvent.dataTransfer.setData('text/plain', 'anything');

            }
        };

        container.onDragOver = function(evt) {
            if (evt.target.getContext) {
                var pixel = evt.target.getContext('2d').getImageData(evt.offsetX, evt.offsetY, 1, 1).data;
                if (pixel[3] === 255) {
                    if (draggable && $(canvas).attr("active") === "true") {
                        var x = settings.x + evt.clientX - prevX;
                        var y = settings.y + evt.clientY - prevY;
                        if (x == settings.x && y == settings.y)
                            return; // position has not changed
                        settings.x += evt.clientX - prevX;
                        settings.y += evt.clientY - prevY;
                        prevX = evt.clientX;
                        prevY = evt.clientY;
                        clearTimeout(timeout);
                        timeout = setTimeout(function() {
                            container.updateStyle();
                            renderInnerImage();
                        }, 20);
                    }
                } else {
                    evt.stopPropagation();
                    return false;
                }
            }
        };

        // end

        container.updateStyle = function() {
            return new Promise((resolve, reject) => {
                context.beginPath();
                context.globalCompositeOperation = "source-over";
                image = new Image();
                image.setAttribute('crossOrigin', 'anonymous');
                image.src = settings.maskImageUrl;
                image.onload = function() {
                    canvas.width = image.width;
                    canvas.height = image.height;
                    context.drawImage(image, 0, 0, image.width, image.height);
                    div.css({
                        "width": image.width,
                        "height": image.height
                    });
                    resolve();
                };
            });
        };

        function renderInnerImage() {
            img = new Image();
            img.setAttribute('crossOrigin', 'anonymous');
            img.src = settings.imageUrl;
            img.onload = function() {
                settings.x = settings.x == 0 && initImage ? (canvas.width - (img.width * settings.scale)) / 2 : settings.x;
                settings.y = settings.y == 0 && initImage ? (canvas.height - (img.height * settings.scale)) / 2 : settings.y;
                context.globalCompositeOperation = 'source-atop';
                context.drawImage(img, settings.x, settings.y, img.width * settings.scale, img.height * settings.scale);
                initImage = false;
            };
        }

        // change the draggable image

        container.loadImage = function(imageUrl) {
            console.log("load");
            settings.y = startY;
            settings.x = startX;
            prevX = prevY = 0;
            settings.imageUrl = imageUrl;
            initImage = true;
            container.updateStyle().then(renderInnerImage);
            // sirpepole  Add this
            return settings.id;
        };

        container.loadMaskImage = function(imageUrl, from) {
            canvas = document.createElement("canvas");
            context = canvas.getContext('2d');
            canvas.setAttribute("draggable", "true");
            canvas.setAttribute("id", settings.id);
            settings.maskImageUrl = imageUrl;
            div = $("<div/>", {
                "class": "masked-img"
            }).append(canvas);

            // div.find("canvas").on('touchstart mousedown', function(event)
            div.find("canvas").on('dragstart', function(event) {
                if (event.handled === false) return;
                event.handled = true;
                container.onDragStart(event);
            });

            div.find("canvas").on('touchend mouseup', function(event) {
                if (event.handled === false) return;
                event.handled = true;
                container.selected(event);
            });

            div.find("canvas").bind("dragover", container.onDragOver);
            container.append(div);
            if (settings.onMaskImageCreate)
                settings.onMaskImageCreate(div);
            container.loadImage(settings.imageUrl);
        };
        container.loadMaskImage(settings.maskImageUrl);
        JQmasks.push({
            item: container,
            id: settings.id
        })
        // Edit image
        div.addClass('masked-img' + settings.id);
        // end
        return container;
    };
}(jQuery));

.container {
	background: silver;
	position: relative;
	
}

.container img {
	position: absolute;
	top: 0;
	bottom: 250px;
	left: 0;
	right: 0;
	margin: auto;
	z-index: 999;
}

.masked-img {
	overflow: hidden;
	position: relative;
}

.pip {
	display: inline-block;
	margin: 0;
	position: absolute;
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js">
</script>

<input id="fileup" name="fileup" type="file" style="display:none" >

<div id="container"class="container">
</div>

Answer 1

我显示了您的代码，并使用JavaScript的超时功能来拖动您的代码。

您的JS中有此代码

container.onDragOver = function(evt) {
    if (evt.target.getContext) {
        var pixel = evt.target.getContext('2d').getImageData(evt.offsetX, evt.offsetY, 1, 1).data;
        if (pixel[3] === 255) {
            if (draggable && $(canvas).attr("active") === "true") {
                var x = settings.x + evt.clientX - prevX;
                var y = settings.y + evt.clientY - prevY;
                if (x == settings.x && y == settings.y)
                    return; // position has not changed
                settings.x += evt.clientX - prevX;
                settings.y += evt.clientY - prevY;
                prevX = evt.clientX;
                prevY = evt.clientY;
                clearTimeout(timeout);
                timeout = setTimeout(function() {
                    container.updateStyle();
                    renderInnerImage();
                }, 20);
            }
        } else {
            evt.stopPropagation();
            return false;
        }
    }
};

只需在下面的代码中替换您所需的时间

timeout = setTimeout(function() {
    container.updateStyle();
    renderInnerImage();
}, 20);

将20替换为1，您的拖动速度将会提高。