Android – Resize video using Renderscript

// resize.rs
#pragma version(1)
#pragma rs java_package_name(com.example)

rs_allocation gIn;
rs_allocation gOut;
int gWidth;
int gHeight;
int gNewWidth;
int gNewHeight;

void resize() {
    float x_ratio = (float)gWidth / gNewWidth;
    float y_ratio = (float)gHeight / gNewHeight;

    for (int y = 0; y < gNewHeight; y++) {
        for (int x = 0; x < gNewWidth; x++) {
            float px = x * x_ratio;
            float py = y * y_ratio;
            rsSetElementAt_uchar(gOut, rsGetElementAt_uchar(gIn, (int)px, (int)py), x, y);
        }
    }
}

// Resizer.kt
package com.videoprocessor

import android.content.Context
import android.renderscript.Allocation
import android.renderscript.RenderScript
import android.renderscript.Script

class Resizer(context: Context) {
    private val renderScript = RenderScript.create(context)
    private val resizeScript = ScriptC_resize(renderScript)

    fun resize(input: Allocation, width: Int, height: Int, newWidth: Int, newHeight: Int): Allocation {
        val tb = Allocation.createTyped(renderScript, input.type)
        val output = Allocation.createTyped(renderScript, tb.type)

        resizeScript.gIn = input
        resizeScript.gOut = output
        resizeScript.gWidth = width
        resizeScript.gHeight = height
        resizeScript.gNewWidth = newWidth
        resizeScript.gNewHeight = newHeight

        resizeScript.forEach_resize(output)
        return output
    }
}

// Example usage in your activity or fragment
val videoResizer = Resizer(this)
val inputAllocation: Allocation = // Allocate the input video frames

val resizedAllocation = videoResizer.resize(
    inputAllocation,
    originalWidth,
    originalHeight,
    newWidth,
    newHeight
)