[java] How to do perspective fixing?

I'm searching for a fast way to fix perspective of a picture given in java or any language.And currently i really don't have any idea how to do it, nor find anything useful in Google.

Input: Point[4] , Color[][]

Output: Perspective-Fixed Color[][]

By Perspective Fixing, i meant the one in Photoshop. Just Like:

I^d appreciate it if you tell me how the code piece works since i want to understand the logic.

This question is related to java math logic perspective

The answer is

The simple solution is to just remap coordinates from the original to the final image, copying pixels from one coordinate space to the other, rounding off as necessary -- which may result in some pixels being copied several times adjacent to each other, and other pixels being skipped, depending on whether you're stretching or shrinking (or both) in either dimension. Make sure your copying iterates through the destination space, so all pixels are covered there even if they're painted more than once, rather than thru the source which may skip pixels in the output.

The better solution involves calculating the corresponding source coordinate without rounding, and then using its fractional position between pixels to compute an appropriate average of the (typically) four pixels surrounding that location. This is essentially a filtering operation, so you lose some resolution -- but the result looks a LOT better to the human eye; it does a much better job of retaining small details and avoids creating straight-line artifacts which humans find objectionable.

Note that the same basic approach can be used to remap flat images onto any other shape, including 3D surface mapping.

Examples related to java

Under what circumstances can I call findViewById with an Options Menu / Action Bar item? How much should a function trust another function How to implement a simple scenario the OO way Two constructors How do I get some variable from another class in Java? this in equals method How to split a string in two and store it in a field How to do perspective fixing? String index out of range: 4 My eclipse won't open, i download the bundle pack it keeps saying error log

Examples related to math

How to do perspective fixing? How to pad a string with leading zeros in Python 3 How can I use "e" (Euler's number) and power operation in python 2.7 numpy max vs amax vs maximum Efficiently getting all divisors of a given number Using atan2 to find angle between two vectors How to calculate percentage when old value is ZERO Finding square root without using sqrt function? Exponentiation in Python - should I prefer ** operator instead of math.pow and math.sqrt? How do I get the total number of unique pairs of a set in the database?

Examples related to logic

How to do perspective fixing? What is the optimal algorithm for the game 2048? ReferenceError: Invalid left-hand side in assignment Prolog "or" operator, query Write code to convert given number into words (eg 1234 as input should output one thousand two hundred and thirty four) JQuery .hasClass for multiple values in an if statement AND/OR in Python? Simple 'if' or logic statement in Python 1 = false and 0 = true? Reference — What does this symbol mean in PHP?

Examples related to perspective

How to do perspective fixing?