Position custom Gui

i try to create a custom gui design for my own Minecraft plugin, but i have two problems.
First, the image is rendering a much darker then the the file is.
Second, the x position is wrong.
{
    "providers": [
        {"type": "bitmap","file":"minecraft:guis/cosmos/workbench.png","ascent": 31, "height": 256,"chars": ["🔨"]}
    ]
}