Pinch and zoom + pan in love2d

main.lua

local lg, lt = love.graphics, love.touch
local insert, remove = table.insert, table.remove
local sqrt = math.sqrt

local x,y, w,h = love.window.getSafeArea()
local textW, textH = x+w,y+h
local a, b = textW/2, textH/2
local texture = lg.newCanvas(textW,textH)
lg.setCanvas(texture)
lg.setColor(.5,.5,.5)
lg.rectangle("fill", 0,0, a,b)
lg.setColor(0,.5,.5)
lg.rectangle("fill", a,0, a,b)
lg.setColor(.5,0,.5)
lg.rectangle("fill", 0,b, a,b)
lg.setColor(.5,.5,0)
lg.rectangle("fill", a,b, a,b)
lg.setCanvas()

local cameraX, cameraY, cameraScale = 0,0, 1
local cameraScaleSpeed = .01
local lastX, lastY

local scaleLimit = {
    low = 0.1,
    high = 2,
}

local touches = {}
local lastDist = 0
local prevWidth, prevHeight = w,h

love.draw = function()
    lg.setColor(1,1,1)
    lg.push()
    lg.scale(cameraScale)
    lg.translate(cameraX, cameraY)
    lg.draw(texture)
    if FX and FY then
        lg.setColor(1,1,0)
        lg.circle("fill", FX, FY, 5)
    end
    lg.pop()
    lg.print(("X: %.2f Y: %.2f\nS: %.2f T: %d\nDist: %.2f\nW: %.2f H: %.2f"):format(cameraX, cameraY, cameraScale, #touches, lastDist, prevWidth, prevHeight), 50,50)
end

local updateTouch = function(touch)
    local lastX, lastY = touch.x, touch.y
    local dx,dy = 0,0
    for k, move in ipairs(touch.moved) do
        dx = dx + (move.x - lastX) / cameraScale
        dy = dy + (move.y - lastY) / cameraScale
        lastX, lastY = move.x, move.y
        touch.moved[k] = nil
    end
    touch.x = lastX
    touch.y = lastY
    return dx, dy
end

love.update = function(dt)
    if #touches == 1 then
        local dx, dy = updateTouch(touches[1])
        
        cameraX = cameraX + dx
        cameraY = cameraY + dy
    elseif #touches == 2 then
        updateTouch(touches[1])
        updateTouch(touches[2])
        local A, B = {}, {}
        A.x, B.x = touches[1].x, touches[2].x
        A.y, B.y = touches[1].y, touches[2].y
        -- Scale
        local dx,dy = B.x - A.x, B.y - A.y
        local dist = sqrt(dx*dx+dy*dy)

        cameraScale = cameraScale * (dist/lastDist)
        if scaleLimit then
            if cameraScale > scaleLimit.high then
                cameraScale = scaleLimit.high
            elseif cameraScale < scaleLimit.low then
                cameraScale = scaleLimit.low
            else
                lastDist = dist
            end
        else
            lastDist = dist
        end
        -- Translate
        A.x, B.x = A.x / cameraScale, A.y / cameraScale
        A.y, B.y = B.x / cameraScale, B.y / cameraScale
        
        local focalX = (A.x + B.x) / 2
        local focalY = (A.y + B.y) / 2
        
        local _,_,w,h = love.window.getSafeArea()
        
        local nextWidth  = w * cameraScale
        local nextHeight = h * cameraScale
        
        cameraX =cameraX+ (-focalX * ((nextWidth - prevWidth) / nextWidth))
        cameraY =cameraY+ (-focalY * ((nextHeight - prevHeight) / nextHeight))
        
        prevWidth, prevHeight = nextWidth, nextHeight
    end
end

local getTouch = function(id)
    for k,v in ipairs(touches) do
        if v.id == id then return k,v end
    end
end

love.touchpressed = function(id, x, y, dx, dy, pressure)
    insert(touches, {id=id, x=x, y=y, moved={}})
    if #touches == 2 then
        local dx, dy = touches[2].x - touches[1].x, touches[2].y - touches[1].y
        lastDist = sqrt(dx*dx+dy*dy)
    end
end

love.touchmoved = function(id, x, y, dx, dy, pressure)
    local _, touch = getTouch(id)
    insert(touch.moved, {x=x, y=y})
end

love.touchreleased = function(id, x, y, dx, dy, pressure)
    remove(touches, getTouch(id))
end

Taken from my code at https://github.com/EngineerSmith/BrushMap/blob/main/input/touch.lua which includes more features

There is an issue with drifting the further you zoom out