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move image using java script and html css

I want to move a image in a path using js and html.
is that doable?
please check the image to get better idea about my question. are there any example codes or libraries? so I can study and edit to match into my case.

There are multiple ways to approach this problem.
Modify html image css styling via javascript.
add css styling via javascript.
styling to move/rotate : transform: translate(20px,10px) rotate(0.5turn);
change styling using pure css animations #keyframes more here
Display stuff on <canvas> element via javascript more here
Animated svg, or svg with css animation.
Inline svg animated via javascript or css.
I am for now just going to demonstrate the svg approach.
SVG approach (no javascript)
My preferred approach would be to create a svg containing multiple images, and then animate it. The bellow example is just using circle objects, but images should work too using <image href="">.
<svg viewBox="0 0 50 50" xmlns="http://www.w3.org/2000/svg" version="1.1" xmlns:xlink="http://www.w3.org/1999/xlink">
<path id="movepath" d="M 5 5 C 10 10, 20 10, 25 5" stroke="#aaa" stroke-width="1" fill="none" />
<circle cx=5 cy=5 r=2 fill="#aaa"/>
<circle cx=25 cy=5 r=2 fill="#aaa"/>
<circle r=1.5 fill="#000">
<animateMotion dur="1s" repeatCount="indefinite">
<mpath xlink:href="#movepath"/>
</animateMotion>
</circle>
</svg>

I don't know if I had understood your question, but I try to answer you.
If I should to do this, "move rocket from earth to sun" I would do it like this:
I'll create 3 img.
img rocket;
img earth;
img sun;
With CSS I will set the Rocket img movement from img earth to sun. Html is not request.

CSS Targeting Individual Paths through SVG -> Use tag

I'm having huge problems animating an ellipsis icon to jiggle the little dots up and down in a wave. I suspect that because its in the shadow DOM I can't target the individual path elements specifically, however is there a work-around?
DOM looks like this:
<svg class="icon__vector">
<use xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="#icon-ellipsis"></use>
</svg>
Where the href link links to this SVG hardcoded in a sprite sheet in which I can edit if needed.
<svg id="icon-ellipsis" width="100%" height="100%" viewBox="0 0 24 24">
<path className="icon-ellipsis-dotone" d="M6 11.59c0 1.105-0.895 2-2 2s-2-0.895-2-2c0-1.105 0.895-2 2-2s2 0.895 2 2z"></path>
<path className="icon-ellipsis-dottwo" d="M14 11.59c0 1.105-0.895 2-2 2s-2-0.895-2-2c0-1.105 0.895-2 2-2s2 0.895 2 2z"></path>
<path className="icon-ellipsis-dotthree" d="M22 11.59c0 1.105-0.895 2-2 2s-2-0.895-2-2c0-1.105 0.895-2 2-2s2 0.895 2 2z"></path>
</svg>
EDIT:
So i have an ellipsis icon something like this "O O O" and i its loaded in with a <use> tag and i want to be able to target each individual dot and animate them differentely. I can edit the master sprite sheet, use javascript or css however no jquery.
Problem is that there is no way to target the individual paths because they exist in the shadow DOM

You can't use CSS or JS to target the referenced elements through the <use>.
You can animate the targeted sprite directly. However that means that, if the SVG is referenced more than once, all those instances will be animated at the same time.

Adapt Div area to Background img size

I haven't found any solution for this problem but I'm sure that one exists.
I have 4 divs with background images, together comprising a graphical option wheel.
The problem is that each div's background image is triangular, but the area that is occupied by the div is bigger and is a square. When I pass the cursor over each div, it is not working well, because the first div overlaps on top of the second, the second over the third, etc.
I thought about using z-index but that won't work because the first and the second div overlap one another, and so do the third and fourth.
I'm not sure if I've explained my problem very well. If you don't understand something, please let me know.
Here is an image to help you understand what I mean.
Thanks!!
UPDATE WITH CODE
Here is my code:
https://jsfiddle.net/ialex90/x7mx1zqu/

You can only achieve this effect with SVG. See the following base implementation that illustrates how you can both apply CSS and JS to irregular shapes using SVG:
$('path').click(function(e) {
alert(e.target.id);
});
path {
stroke:red;
stroke-width:1;
fill:rgba(255,0,0,0.15);
transition:fill 0.5s;
}
path:hover {
fill:rgba(255,0,0,0.5);
}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<svg viewBox="0 0 500 250" width="500" height="250">
<g>
<path id="quadrant1" d="M0,250 A250,250 0 0,1 73,73 L161,161 A125,125 0 0,0 125,250 z" />
<path id="quadrant2" d="M73,73 A250,250 0 0,1 250,0 L250,125 A125,125 0 0,0 161,161 z" />
</g>
</svg>

How to use z-index in svg elements?

I'm using the svg circles in my project like this,
<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 160 120">
<g>
<g id="one">
<circle fill="green" cx="100" cy="105" r="20" />
</g>
<g id="two">
<circle fill="orange" cx="100" cy="95" r="20" />
</g>
</g>
</svg>
And I'm using the z-index in the g tag to show the elements the first. In my project I need to use only z-index value, but I can't use the z-index to my svg elements. I have googled a lot but I didn't find anything relatively.
So please help me to use z-index in my svg.
Here is the DEMO.

Specification
In the SVG specification version 1.1 the rendering order is based on the document order:
first element -> "painted" first
Reference to the SVG 1.1. Specification
3.3 Rendering Order
Elements in an SVG document fragment have an implicit drawing order, with the first elements in the SVG document fragment getting "painted" first. Subsequent elements are painted on top of previously painted elements.
Solution (cleaner-faster)
You should put the green circle as the latest object to be drawn. So swap the two elements.
<svg xmlns="http://www.w3.org/2000/svg" viewBox="30 70 160 120">
<!-- First draw the orange circle -->
<circle fill="orange" cx="100" cy="95" r="20"/>
<!-- Then draw the green circle over the current canvas -->
<circle fill="green" cx="100" cy="105" r="20"/>
</svg>
Here the fork of your jsFiddle.
Solution (alternative)
The tag use with the attribute xlink:href (just href for SVG 2) and as value the id of the element. Keep in mind that might not be the best solution even if the result seems fine. Having a bit of time, here the link of the specification SVG 1.1 "use" Element.
Purpose:
To avoid requiring authors to modify the referenced document to add an ID to the root element.
<svg xmlns="http://www.w3.org/2000/svg" viewBox="30 70 160 120">
<!-- First draw the green circle -->
<circle id="one" fill="green" cx="100" cy="105" r="20" />
<!-- Then draw the orange circle over the current canvas -->
<circle id="two" fill="orange" cx="100" cy="95" r="20" />
<!-- Finally draw again the green circle over the current canvas -->
<use xlink:href="#one"/>
</svg>
Notes on SVG 2
SVG 2 Specification is the next major release and still supports the above features.
3.4. Rendering order
Elements in SVG are positioned in three dimensions. In addition to their position on the x and y axis of the SVG viewport, SVG elements are also positioned on the z axis. The position on the z-axis defines the order that they are painted.
Along the z axis, elements are grouped into stacking contexts.
3.4.1. Establishing a stacking context in SVG
...
Stacking contexts are conceptual tools used to describe the order in which elements must be painted one on top of the other when the document is rendered, ...
SVG 2 Support Mozilla - Painting
How do I know if my browser supports svg 2.0
Can I use SVG
Deprecated XLink namespace For SVG 2 use href instead of the additional deprecated namespace xlink:href (Thanks G07cha)

As others here have said, z-index is defined by the order the element appears in the DOM. If manually reordering your html isn't an option or would be difficult, you can use D3 to reorder SVG groups/objects.
Use D3 to Update DOM Order and Mimic Z-Index Functionality
Updating SVG Element Z-Index With D3
At the most basic level (and if you aren't using IDs for anything else), you can use element IDs as a stand-in for z-index and reorder with those. Beyond that you can pretty much let your imagination run wild.
Examples in code snippet
var circles = d3.selectAll('circle')
var label = d3.select('svg').append('text')
.attr('transform', 'translate(' + [5,100] + ')')
var zOrders = {
IDs: circles[0].map(function(cv){ return cv.id; }),
xPos: circles[0].map(function(cv){ return cv.cx.baseVal.value; }),
yPos: circles[0].map(function(cv){ return cv.cy.baseVal.value; }),
radii: circles[0].map(function(cv){ return cv.r.baseVal.value; }),
customOrder: [3, 4, 1, 2, 5]
}
var setOrderBy = 'IDs';
var setOrder = d3.descending;
label.text(setOrderBy);
circles.data(zOrders[setOrderBy])
circles.sort(setOrder);
<script src="https://cdnjs.cloudflare.com/ajax/libs/d3/3.4.11/d3.min.js"></script>
<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 400 100">
<circle id="1" fill="green" cx="50" cy="40" r="20"/>
<circle id="2" fill="orange" cx="60" cy="50" r="18"/>
<circle id="3" fill="red" cx="40" cy="55" r="10"/>
<circle id="4" fill="blue" cx="70" cy="20" r="30"/>
<circle id="5" fill="pink" cx="35" cy="20" r="15"/>
</svg>
The basic idea is:
Use D3 to select the SVG DOM elements.
var circles = d3.selectAll('circle')
Create some array of z-indices with a 1:1 relationship with your SVG elements (that you want to reorder). Z-index arrays used in the examples below are IDs, x & y position, radii, etc....
var zOrders = {
IDs: circles[0].map(function(cv){ return cv.id; }),
xPos: circles[0].map(function(cv){ return cv.cx.baseVal.value; }),
yPos: circles[0].map(function(cv){ return cv.cy.baseVal.value; }),
radii: circles[0].map(function(cv){ return cv.r.baseVal.value; }),
customOrder: [3, 4, 1, 2, 5]
}
Then, use D3 to bind your z-indices to that selection.
circles.data(zOrders[setOrderBy]);
Lastly, call D3.sort to reorder the elements in the DOM based on the data.
circles.sort(setOrder);
Examples
You can stack by ID
With leftmost SVG on top
Smallest radii on top
Or Specify an array to apply z-index for a specific ordering -- in my example code the array [3,4,1,2,5] moves/reorders the 3rd circle (in the original HTML order) to be 1st in the DOM, 4th to be 2nd, 1st to be 3rd, and so on...

Try to invert #one and #two. Have a look to this fiddle : http://jsfiddle.net/hu2pk/3/
Update
In SVG, z-index is defined by the order the element appears in the document. You can have a look to this page too if you want : https://stackoverflow.com/a/482147/1932751

You can use use.
<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 160 120">
<g>
<g id="one">
<circle fill="green" cx="100" cy="105" r="20" />
</g>
<g id="two">
<circle fill="orange" cx="100" cy="95" r="20" />
</g>
</g>
<use xlink:href="#one" />
</svg>
The green circle appears on top.
jsFiddle

As discussed, svgs render in order and don't take z-index into account (for now). Maybe just send the specific element to the bottom of its parent so that it'll render last.
function bringToTop(targetElement){
// put the element at the bottom of its parent
let parent = targetElement.parentNode;
parent.appendChild(targetElement);
}
// then just pass through the element you wish to bring to the top
bringToTop(document.getElementById("one"));
Worked for me.
Update
If you have a nested SVG, containing groups, you'll need to bring the item out of its parentNode.
function bringToTopofSVG(targetElement){
let parent = targetElement.ownerSVGElement;
parent.appendChild(targetElement);
}
A nice feature of SVG's is that each element contains it's location regardless of what group it's nested in :+1:

Using D3:
If you want to re-inserts each selected element, in order, as the last child of its parent.
selection.raise()

Using D3:
If you want to add the element in the reverse order to the data, use:
.insert('g', ":first-child")
Instead of .append('g')
Adding an element to top of a group element

There is no z-index for svgs. But svg determines which of your elements are the uppermost by theire position in the DOM. Thus you can remove the Object and place it to the end of the svg making it the "last rendered" element. That one is then rendered "topmost" visually.
Using jQuery:
function moveUp(thisObject){
thisObject.appendTo(thisObject.parents('svg>g'));
}
usage:
moveUp($('#myTopElement'));
Using D3.js:
d3.selection.prototype.moveUp = function() {
return this.each(function() {
this.parentNode.appendChild(this);
});
};
usage:
myTopElement.moveUp();

This is the top Google result for searches regarding z-index and SVGs. After reading all the answers, some of which are very good, I was still confused.
So for rookies like me, here is the current summary, 9 years later in 2022.
You can't use z-index with SVGs.
In SVGs, z-index is defined by the order the element appears in the document.
If you want something to appear on top, or closer to the user, draw it last or insert it before. Source
SVG 2 could support z-index but might never come out
SVG 2 is a proposal to implement that and other features but it is at risk of never moving forward.
SVG 2 reached the Candidate Recommendation stage in 2016, and was revised in 2018 and the latest draft was released on 8 June 2021. Source
However it doesn't have a lot of support and very few people are working on it. Source So don't hold your breath waiting for this.
You could use D3 but probably shouldn't
D3 a commonly used to visualize data supports z-index by binding your z-index and then sorting but it is a large and complex library and might not be the best bet if you just want a certain SVG to appear on top of a stack.

The clean, fast, and easy solutions posted as of the date of this answer are unsatisfactory. They are constructed over the flawed statement that SVG documents lack z order. Libraries are not necessary either. One line of code can perform most operations to manipulate the z order of objects or groups of objects that might be required in the development of an app that moves 2D objects around in an x-y-z space.
Z Order Definitely Exists in SVG Document Fragments
What is called an SVG document fragment is a tree of elements derived from the base node type SVGElement. The root node of an SVG document fragment is an SVGSVGElement, which corresponds to an HTML5 <svg> tag. The SVGGElement corresponds to the <g> tag and permits aggregating children.
Having a z-index attribute on the SVGElement as in CSS would defeat the SVG rendering model. Sections 3.3 and 3.4 of W3C SVG Recommendation v1.1 2nd Edition state that SVG document fragments (trees of offspring from an SVGSVGElement) are rendered using what is called a depth first search of the tree. That scheme is a z order in every sense of the term.
Z order is actually a computer vision shortcut to avoid the need for true 3D rendering with the complexities and computing demands of ray tracing. The linear equation for the implicit z-index of elements in an SVG document fragment.
z-index = z-index_of_svg_tag + depth_first_tree_index / tree_node_qty
This is important because if you want to move a circle that was below a square to above it, you simply insert the square before the circle. This can be done easily in JavaScript.
Supporting Methods
SVGElement instances have two methods that support simple and easy z order manipulation.
parent.removeChild(child)
parent.insertBefore(child, childRef)
The Correct Answer That Doesn't Create a Mess
Because the SVGGElement (<g> tag) can be removed and inserted just as easily as a SVGCircleElement or any other shape, image layers typical of Adobe products and other graphics tools can be implemented with ease using the SVGGElement. This JavaScript is essentially a Move Below command.
parent.insertBefore(parent.removeChild(gRobot), gDoorway)
If the layer of a robot drawn as children of SVGGElement gRobot was before the doorway drawn as children of SVGGElement gDoorway, the robot is now behind the doorway because the z order of the doorway is now one plus the z order of the robot.
A Move Above command is almost as easy.
parent.insertBefore(parent.removeChild(gRobot), gDoorway.nextSibling())
Just think a=a and b=b to remember this.
insert after = move above
insert before = move below
Leaving the DOM in a State Consistent With the View
The reason this answer is correct is because it is minimal and complete and, like the internals of Adobe products or other well designed graphics editors, leaves the internal representation in a state that is consistent with the view created by rendering.
Alternative But Limited Approach
Another approach commonly used is to use CSS z-index in conjunction with multiple SVG document fragments (SVG tags) with mostly transparent backgrounds in all but the bottom one. Again, this defeats the elegance of the SVG rendering model, making it difficult to move objects up or down in the z order.
NOTES:
(https://www.w3.org/TR/SVG/render.html v 1.1, 2nd Edition, 16 August 2011)
3.3 Rendering Order Elements in an SVG document fragment have an implicit drawing order, with the first elements in the SVG document
fragment getting "painted" first. Subsequent elements are painted on
top of previously painted elements.
3.4 How groups are rendered Grouping elements such as the ‘g’ element (see container elements) have the effect of producing a temporary
separate canvas initialized to transparent black onto which child
elements are painted. Upon the completion of the group, any filter
effects specified for the group are applied to create a modified
temporary canvas. The modified temporary canvas is composited into the
background, taking into account any group-level masking and opacity
settings on the group.

Another solution would be to use divs, which do use zIndex to contain the SVG elements.As here:
https://stackoverflow.com/a/28904640/4552494

We have already 2019 and z-index is still not supported in SVG.
You can see on the site SVG2 support in Mozilla that the state for z-index – Not implemented.
You can also see on the site Bug 360148 "Support the 'z-index' property on SVG elements" (Reported: 12 years ago).
But you have 3 possibilities in SVG to set it:
With element.appendChild(aChild);
With parentNode.insertBefore(newNode, referenceNode);
With targetElement.insertAdjacentElement(positionStr, newElement); (No support in IE for SVG)
Interactive demo example
With all this 3 functions.
var state = 0,
index = 100;
document.onclick = function(e)
{
if(e.target.getAttribute('class') == 'clickable')
{
var parent = e.target.parentNode;
if(state == 0)
parent.appendChild(e.target);
else if(state == 1)
parent.insertBefore(e.target, null); //null - adds it on the end
else if(state == 2)
parent.insertAdjacentElement('beforeend', e.target);
else
e.target.style.zIndex = index++;
}
};
if(!document.querySelector('svg').insertAdjacentElement)
{
var label = document.querySelectorAll('label')[2];
label.setAttribute('disabled','disabled');
label.style.color = '#aaa';
label.style.background = '#eee';
label.style.cursor = 'not-allowed';
label.title = 'This function is not supported in SVG for your browser.';
}
label{background:#cef;padding:5px;cursor:pointer}
.clickable{cursor:pointer}
With:
<label><input type="radio" name="check" onclick="state=0" checked/>appendChild()</label>
<label><input type="radio" name="check" onclick="state=1"/>insertBefore()</label><br><br>
<label><input type="radio" name="check" onclick="state=2"/>insertAdjacentElement()</label>
<label><input type="radio" name="check" onclick="state=3"/>Try it with z-index</label>
<br>
<svg width="150" height="150" viewBox="0 0 150 150">
<g stroke="none">
<rect id="i1" class="clickable" x="10" y="10" width="50" height="50" fill="#80f"/>
<rect id="i2" class="clickable" x="40" y="40" width="50" height="50" fill="#8f0"/>
<rect id="i3" class="clickable" x="70" y="70" width="50" height="50" fill="#08f"/>
</g>
</svg>

Push SVG element to last, so that its z-index will be in top. In SVG, there s no property called z-index. try below javascript to bring the element to top.
var Target = document.getElementById(event.currentTarget.id);
var svg = document.getElementById("SVGEditor");
svg.insertBefore(Target, svg.lastChild.nextSibling);
Target: Is an element for which we need to bring it to top
svg: Is the container of elements

Move to front by transform:TranslateZ
Warning: Only works in FireFox
<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 160 160" style="width:160px; height:160px;">
<g style="transform-style: preserve-3d;">
<g id="one" style="transform-style: preserve-3d;">
<circle fill="green" cx="100" cy="105" r="20" style="transform:TranslateZ(1px);"></circle>
</g>
<g id="two" style="transform-style: preserve-3d;">
<circle fill="orange" cx="100" cy="95" r="20"></circle>
</g>
</g>
</svg>

A better example of use, that I've ended up using.
<svg>
<defs>
<circle id="one" fill="green" cx="40" cy="40" r="20" />
<circle id="two" fill="orange" cx="50" cy="40" r="20"/>
</defs>
<use href="#two" />
<use href="#one" />
</svg>
To control the order you can change href attribute values of these use elements. This can be useful for animation.
Thanks to defs, circle elements are drawn only once.
jsfiddle.net/7msv2w5d

its easy to do it:
clone your items
sort cloned items
replace items by cloned
function rebuildElementsOrder( selector, orderAttr, sortFnCallback ) {
let $items = $(selector);
let $cloned = $items.clone();
$cloned.sort(sortFnCallback != null ? sortFnCallback : function(a,b) {
let i0 = a.getAttribute(orderAttr)?parseInt(a.getAttribute(orderAttr)):0,
i1 = b.getAttribute(orderAttr)?parseInt(b.getAttribute(orderAttr)):0;
return i0 > i1?1:-1;
});
$items.each(function(i, e){
e.replaceWith($cloned[i]);
})
}
$('use[order]').click(function() {
rebuildElementsOrder('use[order]', 'order');
/* you can use z-index property for inline css declaration
** getComputedStyle always return "auto" in both Internal and External CSS decl [tested in chrome]
rebuildElementsOrder( 'use[order]', null, function(a, b) {
let i0 = a.style.zIndex?parseInt(a.style.zIndex):0,
i1 = b.style.zIndex?parseInt(b.style.zIndex):0;
return i0 > i1?1:-1;
});
*/
});
use[order] {
cursor: pointer;
}
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" id="keybContainer" viewBox="0 0 150 150" xml:space="preserve">
<defs>
<symbol id="sym-cr" preserveAspectRatio="xMidYMid meet" viewBox="0 0 60 60">
<circle cx="30" cy="30" r="30" />
<text x="30" y="30" text-anchor="middle" font-size="0.45em" fill="white">
<tspan dy="0.2em">Click to reorder</tspan>
</text>
</symbol>
</defs>
<use order="1" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="#sym-cr" x="0" y="0" width="60" height="60" style="fill: #ff9700; z-index: 1;"></use>
<use order="4" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="#sym-cr" x="50" y="20" width="50" height="50" style="fill: #0D47A1; z-index: 4;"></use>
<use order="5" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="#sym-cr" x="15" y="30" width="50" height="40" style="fill: #9E9E9E; z-index: 5;"></use>
<use order="3" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="#sym-cr" x="25" y="30" width="80" height="80" style="fill: #D1E163; z-index: 3;"></use>
<use order="2" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="#sym-cr" x="30" y="0" width="50" height="70" style="fill: #00BCD4; z-index: 2;"></use>
<use order="0" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="#sym-cr" x="5" y="5" width="100" height="100" style="fill: #E91E63; z-index: 0;"></use>
</svg>

Just wanted to add a trick that works when you want to put a specific element on top.
function moveInFront(element) {
const svg = element.closest('svg'); // Find the parent SVG
svg.appendChild(element); // Append child moves the element to the end
}
This works because, and I quote the docs, "appendChild() moves [the element] from its current position to the new position" instead of adding a copy.
Note: If the element is nested, you would have to move the element to front within the group, and perhaps move the group to front as well.

use works for this purpose, but those elements that are placed with use help after is hard to manipulate...
What I couldn't figure out after I used it was: why I couldn't hover (neither mouseover, mouseenter manipulations from js would work) on the use elements to get additional functionality - like ~ showing text over the circles ~
After returned to circle reordering as it was only way to manipulate with those svg objects

Is it possible to linear-gradient-fill a grouped path in SVG (by css or attr on jQuery event)

How can i fill one gradient for a <g> in an SVG image instead of fill all the <g>s in the selected <g>?
In this case, I'd like to show africa, filled with just one gradient from yellow to red, but because of the sub-groups the fill makes many of gradients.
The javascript:
<script type="text/javascript">
function svgOver() {
var what = $(this).attr("id");
$("#world #"+what, svg.root()).attr("fill", "url(#red_black)");
}
function svgOut() {
$(this).attr("fill", "");
}
...
$("#map").svg({
loadURL: 'http://teszt.privilegetours.hu/skins/privilege/svg/worldmap.svg',
onLoad: function(svg) {
$("#world > g", svg.root()).bind('mouseover', svgOver).bind('mouseout', svgOut).bind('click', svgZoom);
},
settings: {}
});
The SVG:
<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
<svg version="1.1" id="Layer_1" xmlns="http://www.w3.org/2000/svg" mlns:xlink="http://www.w3.org/1999/xlink" x="0px" y="0px" width="570px" height="300px" viewBox="146.605 71.42 570 300" enable-background="new 146.605 71.42 570 300" xml:space="preserve">
<defs>
<linearGradient id="red_black" x1="0%" y1="0%" x2="0%" y2="100%">
<stop offset="0%" style="stop-color:rgb(255,0,0);stop-opacity:1"/>
<stop offset="100%" style="stop-color:rgb(255,255,0);stop-opacity:1"/>
</linearGradient>
</defs>
<g id="world" transform="scale(1)" fill="#AAAAAA" stroke="#FFFFFF" stroke-width="0.1">
<g id="africa" name="africa"> // < i want to fill this
<g id="er" transform="translate(-29.9017, -45.0745)"> // < instead of theese
<path d="..."/>
</g>
<g id="yt"> // < instead of theese
<path d="..."/>
</g>
...
How can I fix this problem?
How can I fix this problem without adding an another <g> tag to the original image?

your problem can be solved by setting the gradients coordinate system to user space (instead of the default object-bounding box).
you might try
<defs>
<linearGradient id="red_black" x1="0%" y1="0%" x2="0%" y2="100%" gradientUnits="userSpaceOnUse">
<stop offset="0%" style="stop-color:rgb(255,0,0);stop-opacity:1"/>
<stop offset="100%" style="stop-color:rgb(255,255,0);stop-opacity:1"/>
</linearGradient>
</defs>
the solution does not defy the comment by e.nelson - what happens here is that each subgroup representing the nations still has its individual gradient instance applied while all these instances share the same coord origin and the same transformations w.r.t the user space - so at any point in the final rendering, it doesn't matter which gradient instance is visible.
two adjustments are required:
[ minor]
you have to adjust the y1/y2 offsets (or the stop offsets) of the gradient definition - as they refer to the user coord space of the whole map, africa only covers a portion of the gradient between the stops defined. try y1="50%" and y2="100%".
[medium]
if you have a look at svg g-elements defining the country shapes you'll note that some of them are subjected to an additional translation. they effectively shift the user coordinate system and therefore also apply to the gradient which causes the affected country shapes to appear like blotches on the map.
this spurios transform is probably an artefact of the actions in the generator used to create the map.
it can be remedied by adding the translation offsets to each absolute coordinate in the path elements inside the respective g-elements. as these paths are defined using relative coordinates for the pieces stitched together, this reduces to altering the coords of the initial 'M' and final 'C' commands in the path's d-attribute.
i have cooked up an ad hoc perl script to normalize the structure of the svg code representing the country borders that implements the abovementioned modifications. note that these alterations can be done rather conveniently in js too. This is the result.
hope that helps and drop me a note if you need additional informations on how to perform the adjustments mentioned.
PS:
i just noticed that mozambique is still missing from the generated output - for that single country's shape yet another translation has been specified. this minor detail is something to be added later today, however ...

"Painting, however, is always done on each graphics element individually, never at the container element (e.g., a 'g') level. Thus, for the following SVG, even though the gradient fill is specified on the 'g', the gradient is simply inherited through the 'g' element down into each rectangle, each of which is rendered such that its interior is painted with the gradient."
http://www.w3.org/TR/SVGTiny12/painting.html#InheritanceOfPaintingProperties
What you're asking for isn't possible, according to the spec. If it's a requirement, you could explore one of: having the SVG creator add mouse over paths for you; combine the paths in code on the server (potentially tricky); choose a solid color instead of a gradient so the problem isn't so obvious.

If you want to fill all of Africa with one gradient, then you want the union the paths for that fill. Maybe you should use a different map? One with only the continents?
Anyway one way to fix it would be to:
open it up in Inkscape
select all the paths that you want to fill
choose "Union" from the "Path" menu
save the file (or copy&paste the unioned path)
Another way:
Look for another map, see http://d-maps.com/ or http://commons.wikimedia.org. Here's one with the continents only, africa marked.
After doing that you can apply the gradient to that new path.
You could also do it in some other ways, but they're probably not as good for performance reasons. One of those (not recommended) ways would be to fill a rectangle with the gradient where you've made a clip-path consisting of the paths in the group. Something along these lines:
<clipPath id="clip">
<use xlink:href="#africa"/>
</clipPath>
<rect width="100" height="100" fill="url(#grad)" clip-path="url(#clip)"/>
<g id="africa">...</g>

I think your problem might be that fill is inherited according to the standard rules of CSS in SVG. So you'd need to set an explicit fill of transparent on the child g elements. If it's not that I'll come back and have another look after you've got an online example.