Antonsson scored 22 goals in 40 league games for Kalmar after signing from Halmstads in January 2015.
The 25-year-old is Leeds head coach Garry Monk's first signing since replacing Steve Evans on 2 June.
"He scores goals, has great movement and he has the mentality to be able to adapt to this league," Monk said.
"The club has watched a lot of him, I've watched a lot of him and I felt he'd be a good fit for Leeds United."
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For 10 days from 29 April 1945, Operation Manna dropped nearly 7,000 tonnes of food over The Netherlands.
The country had lost 20,000 people through starvation, with a further 980,000 classed as malnourished.
The bulbs were donated by the Dutch government to the International Bomber Command Centre (IBCC).
A ceremony at the cathedral to unveil the mosaic was attended by representatives from The Netherlands, Canada, Australia, New Zealand, Poland, Germany and the US.
Bomber Command veterans also met with some who had been helped by the campaign.
Nicky Barr, from the IBCC, an education facility being built in Lincoln, said Operation Manna was the difference between "people living or dying".
The mission followed a blockade of supplies by German forces in retaliation for Dutch rail companies going on strike in support of an Allied offensive, she said.
The winter of 1944/45 was also particularly harsh, compounding the problem of food shortages.
David Fellows, who flew missions from RAF Binbrook in Lincolnshire as part of Operation Manna, said: "We used to go across to Holland every fifth year and we used to get hugs from young children who would say 'thank you for saving my grandmother', but to meet some of the people who were there at the time is highly emotional."
Recalling the missions, he said: "We knew there were thousands of Dutch people dying - and they were in dire straits."
He said despite concerns the Germans "could open fire on us, the RAF being the RAF took the decision to fly anyway".
He added he was proud to have been part of such an important campaign.

The 20-year-old had "cardiac arrhythmias" - heart rhythm problems - during the game against Werder Bremen.
The club statement said the chances of recovery from the damage is nil.
It added: "The diagnosis was made that a lot of [his] brain is not functioning. All this probably occurred due to a lack of oxygen supply."
On Monday, the club had said tests showed his "heart is functioning normally" and brain scans did not detect "any anomalies" - but new tests revealed the extent of the damage.
The Amsterdam-born player was flown by helicopter to hospital in Austria - where the abandoned friendly match was being played.
Ajax say he will soon be transferred to a hospital in Amsterdam for further care.
Former Manchester United and Fulham goalkeeper Edwin van der Sar, now CEO at Ajax, said: "This is the worst possible message. It is terrible. We feel enormously for his parents, siblings and other relatives.
"The blow is also difficult for Ajax, though we knew we had to consider this scenario. They were uncertain days, lots of people in different ways have sympathised with his situation and is greatly appreciated.
"Abdelhak is such a great talent, but unfortunately we will never know how far his star would have reached had this not happened. "
Nouri played 15 league and cup games for Ajax in 2016-17, scoring one goal in a Dutch Cup tie.
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Championship club Leeds United have signed striker Marcus Antonsson from Swedish top-flight side Kalmar on a three-year deal for an undisclosed fee.
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A floral mosaic showing a Lancaster bomber dropping food supplies in Nazi-occupied Holland has been unveiled at Lincoln Cathedral.
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Ajax midfielder Abdelhak Nouri suffered "serious and permanent brain damage" after collapsing in a friendly match on Saturday.