Implement ResourcePackImageScaler (a class by @prplz) in mcp

ResourcePackImageScaler.java

import java.awt.Graphics;
import java.awt.image.BufferedImage;

public class ResourcePackImageScaler {

    public static final int SIZE = 64;

    public static BufferedImage scalePackImage(BufferedImage image) {
        if (image == null) {
            return null;
        }

        if (image.getWidth() == image.getHeight() && image.getWidth() < SIZE) return image; // avoid scaling up images

        System.out.println("Scaling resource pack icon from " + image.getWidth() + " to " + SIZE);
        BufferedImage smallImage = new BufferedImage(SIZE, SIZE, BufferedImage.TYPE_INT_ARGB);
        Graphics graphics = smallImage.getGraphics();
        graphics.drawImage(image, 0, 0, SIZE, SIZE, null);
        graphics.dispose();
        return smallImage;
    }
}

ResourcePackImageScaler.patch

//create the class ResourcePackImageScaler.java from https://github.com/prplz/MemoryFix/blob/master/src/main/java/io/prplz/memoryfix/ResourcePackImageScaler.java
//go to net.minecraft.client.resources.ResourcePackRepository.Entry
//find the method named updateResourcePack()
        public void updateResourcePack() throws IOException
        {
            this.reResourcePack = (IResourcePack)(this.resourcePackFile.isDirectory() ? new FolderResourcePack(this.resourcePackFile) : new FileResourcePack(this.resourcePackFile));
            this.rePackMetadataSection = (PackMetadataSection)this.reResourcePack.getPackMetadata(ResourcePackRepository.this.rprMetadataSerializer, "pack");

            try
            {
-                this.texturePackIcon = this.reResourcePack.getPackImage();
+                this.texturePackIcon = ResourcePackImageScaler.scalePackImage(this.reResourcePack.getPackImage());
            }
            catch (IOException var2)
            {
                ;
            }

            if (this.texturePackIcon == null)
            {
                this.texturePackIcon = ResourcePackRepository.this.rprDefaultResourcePack.getPackImage();
            }

            this.closeResourcePack();
        }