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🏁 随机位图生成器（噪点图）Random Bitmap Generator
生成指定尺寸的随机像素图：黑白噪点、灰度噪点或彩色噪点，可调黑色比例和像素放大倍数，下载为 PNG 或 24 位 BMP。用于测试图片、纹理、二维码干扰背景和压缩实验。Make random pixel images of any size — black-and-white, greyscale or colour noise — with an adjustable black ratio and pixel scale, downloadable as PNG or 24-bit BMP. Useful for test images, textures and compression experiments.
使用说明与常见问题How-to & FAQ
「随机位图生成器（噪点图）」是什么？What is the Random Bitmap Generator tool?
生成指定尺寸的随机像素图：黑白噪点、灰度噪点或彩色噪点，可调黑色比例和像素放大倍数，下载为 PNG 或 24 位 BMP。用于测试图片、纹理、二维码干扰背景和压缩实验。Make random pixel images of any size — black-and-white, greyscale or colour noise — with an adjustable black ratio and pixel scale, downloadable as PNG or 24-bit BMP. Useful for test images, textures and compression experiments.
如何使用「随机位图生成器（噪点图）」？How do I use the Random Bitmap Generator tool?
在「随机位图生成器（噪点图）」中，按需设置「宽（像素）」、「高（像素）」、「类型」、「黑色比例 %」、「显示放大」等选项，然后点击「生成」、「下载 PNG」、「下载 BMP」按钮即可。In the Random Bitmap Generator: Set "Width (px)", "Height (px)", "Type", "Black %", "Display scale", then click "Generate", "Download PNG", "Download BMP".
BMP 和 PNG 有什么区别？What is the difference between BMP and PNG?
PNG 是无损压缩格式，文件较小；BMP 是不压缩的 24 位位图（每像素 3 字节，每行补齐到 4 字节），文件大但结构简单，常用于测试图像处理程序。PNG 由本工具直接编码，像素值与生成结果完全一致：黑白和灰度图保存为 8 位灰度 PNG，4 色图保存为调色板 PNG，彩色图保存为 24 位 RGB PNG。彩色噪点几乎无法压缩，PNG 和 BMP 大小相近；黑白、灰度和 4 色噪点每像素信息少，PNG 会明显小于 BMP（例如 512×512 黑白图只有 BMP 的几分之一）。PNG is losslessly compressed; BMP here is uncompressed 24-bit (3 bytes per pixel, rows padded to 4 bytes) — large but simple, so it is popular for testing image code. The tool encodes the PNG itself, so its pixels match the generated image exactly: black-and-white and greyscale images are saved as 8-bit greyscale PNG, the 4-colour image as a palette PNG and colour noise as 24-bit RGB. Colour noise barely compresses, so its PNG is about the size of the BMP; black-and-white, greyscale and 4-colour noise carry less information per pixel, so their PNGs are much smaller than the BMP (a 512 × 512 black-and-white image is a fraction of the BMP size).
黑色比例是精确的吗？Is the black ratio exact?
每个像素独立地以设定概率变黑，所以实际比例会在设定值附近浮动；像素越多越接近，例如 100×100 的图在 50% 时标准差约 0.5%，绝大多数情况（3 个标准差）误差在 ±1.5% 以内。Each pixel turns black independently with that probability, so the actual share varies around the setting and gets closer with more pixels — for 100 × 100 at 50% the standard deviation is about 0.5%, so it is almost always (3 standard deviations) within ±1.5%.
显示放大会影响下载的图片吗？Does the display scale change the download?
不会。放大只是让小图在屏幕上看得清楚（使用像素化缩放）；下载的 PNG/BMP 始终是你设定的原始宽高。No. Scaling only makes small images visible on screen (with pixelated rendering); the PNG or BMP you download always has the exact width and height you set.
随机结果真的随机吗？Is the randomness truly random?
「随机位图生成器（噪点图）」使用浏览器的 crypto.getRandomValues（密码学安全随机数）生成随机数据，不使用可预测的 Math.random。The Random Bitmap Generator uses crypto.getRandomValues (cryptographically secure randomness), not the predictable Math.random.
「随机位图生成器（噪点图）」免费吗？需要注册吗？Is the Random Bitmap Generator free? Do I need an account?
「随机位图生成器（噪点图）」完全免费，无需注册或安装，打开网页即可使用，手机和电脑都能用；输入的内容只在你的浏览器本地处理。The Random Bitmap Generator is completely free with no sign-up or install and works on phones and desktops; what you enter is processed only in your browser.