Code/net/minecraft/client/renderer/texture/MipmapGenerator.java

package net.minecraft.client.renderer.texture;

import com.mojang.blaze3d.platform.NativeImage;
import net.minecraft.Util;
import net.minecraft.util.ARGB;
import net.minecraftforge.api.distmarker.Dist;
import net.minecraftforge.api.distmarker.OnlyIn;

@OnlyIn(Dist.CLIENT)
public class MipmapGenerator {
    private static final int ALPHA_CUTOUT_CUTOFF = 96;
    private static final float[] POW22 = Util.make(new float[256], p_118058_ -> {
        for (int i = 0; i < p_118058_.length; i++) {
            p_118058_[i] = (float)Math.pow(i / 255.0F, 2.2);
        }
    });

    private MipmapGenerator() {
    }

    public static NativeImage[] generateMipLevels(NativeImage[] p_251300_, int p_252326_) {
        if (p_252326_ + 1 <= p_251300_.length) {
            return p_251300_;
        } else {
            NativeImage[] anativeimage = new NativeImage[p_252326_ + 1];
            anativeimage[0] = p_251300_[0];
            boolean flag = hasTransparentPixel(anativeimage[0]);

            for (int i = 1; i <= p_252326_; i++) {
                if (i < p_251300_.length) {
                    anativeimage[i] = p_251300_[i];
                } else {
                    NativeImage nativeimage = anativeimage[i - 1];
                    NativeImage nativeimage1 = new NativeImage(nativeimage.getWidth() >> 1, nativeimage.getHeight() >> 1, false);
                    int j = nativeimage1.getWidth();
                    int k = nativeimage1.getHeight();

                    for (int l = 0; l < j; l++) {
                        for (int i1 = 0; i1 < k; i1++) {
                            nativeimage1.setPixel(
                                l,
                                i1,
                                alphaBlend(
                                    nativeimage.getPixel(l * 2 + 0, i1 * 2 + 0),
                                    nativeimage.getPixel(l * 2 + 1, i1 * 2 + 0),
                                    nativeimage.getPixel(l * 2 + 0, i1 * 2 + 1),
                                    nativeimage.getPixel(l * 2 + 1, i1 * 2 + 1),
                                    flag
                                )
                            );
                        }
                    }

                    anativeimage[i] = nativeimage1;
                }
            }

            return anativeimage;
        }
    }

    private static boolean hasTransparentPixel(NativeImage p_252279_) {
        for (int i = 0; i < p_252279_.getWidth(); i++) {
            for (int j = 0; j < p_252279_.getHeight(); j++) {
                if (ARGB.alpha(p_252279_.getPixel(i, j)) == 0) {
                    return true;
                }
            }
        }

        return false;
    }

    private static int alphaBlend(int p_118049_, int p_118050_, int p_118051_, int p_118052_, boolean p_118053_) {
        if (p_118053_) {
            float f = 0.0F;
            float f1 = 0.0F;
            float f2 = 0.0F;
            float f3 = 0.0F;
            if (p_118049_ >> 24 != 0) {
                f += getPow22(p_118049_ >> 24);
                f1 += getPow22(p_118049_ >> 16);
                f2 += getPow22(p_118049_ >> 8);
                f3 += getPow22(p_118049_ >> 0);
            }

            if (p_118050_ >> 24 != 0) {
                f += getPow22(p_118050_ >> 24);
                f1 += getPow22(p_118050_ >> 16);
                f2 += getPow22(p_118050_ >> 8);
                f3 += getPow22(p_118050_ >> 0);
            }

            if (p_118051_ >> 24 != 0) {
                f += getPow22(p_118051_ >> 24);
                f1 += getPow22(p_118051_ >> 16);
                f2 += getPow22(p_118051_ >> 8);
                f3 += getPow22(p_118051_ >> 0);
            }

            if (p_118052_ >> 24 != 0) {
                f += getPow22(p_118052_ >> 24);
                f1 += getPow22(p_118052_ >> 16);
                f2 += getPow22(p_118052_ >> 8);
                f3 += getPow22(p_118052_ >> 0);
            }

            f /= 4.0F;
            f1 /= 4.0F;
            f2 /= 4.0F;
            f3 /= 4.0F;
            int i1 = (int)(Math.pow(f, 0.45454545454545453) * 255.0);
            int j1 = (int)(Math.pow(f1, 0.45454545454545453) * 255.0);
            int k1 = (int)(Math.pow(f2, 0.45454545454545453) * 255.0);
            int l1 = (int)(Math.pow(f3, 0.45454545454545453) * 255.0);
            if (i1 < 96) {
                i1 = 0;
            }

            return ARGB.color(i1, j1, k1, l1);
        } else {
            int i = gammaBlend(p_118049_, p_118050_, p_118051_, p_118052_, 24);
            int j = gammaBlend(p_118049_, p_118050_, p_118051_, p_118052_, 16);
            int k = gammaBlend(p_118049_, p_118050_, p_118051_, p_118052_, 8);
            int l = gammaBlend(p_118049_, p_118050_, p_118051_, p_118052_, 0);
            return ARGB.color(i, j, k, l);
        }
    }

    private static int gammaBlend(int p_118043_, int p_118044_, int p_118045_, int p_118046_, int p_118047_) {
        float f = getPow22(p_118043_ >> p_118047_);
        float f1 = getPow22(p_118044_ >> p_118047_);
        float f2 = getPow22(p_118045_ >> p_118047_);
        float f3 = getPow22(p_118046_ >> p_118047_);
        float f4 = (float)((float)Math.pow((f + f1 + f2 + f3) * 0.25, 0.45454545454545453));
        return (int)(f4 * 255.0);
    }

    private static float getPow22(int p_118041_) {
        return POW22[p_118041_ & 0xFF];
    }
}