🖼️ PDF 转 BMPPDF to BMP Converter

使用说明与常见问题How-to & FAQ

「PDF 转 BMP」是什么？What is the PDF to BMP Converter tool?

把 PDF 每一页转换成 24 位 BMP 位图：可选 72–600 DPI 和页码范围，白色背景、无压缩，适合老式软件、工控设备、嵌入式屏幕和需要 BMP 的打印/刻字程序，多页可打包 ZIP，本地完成。Convert each PDF page into an uncompressed 24-bit BMP bitmap at 72–600 DPI with a page range — for legacy software, industrial and embedded displays, and cutting or printing programs that require BMP. Multi-page results download as a ZIP; fully local.

如何使用「PDF 转 BMP」？How do I use the PDF to BMP Converter tool?

在「PDF 转 BMP」中，按需设置「分辨率」、「页码（留空为全部）」等选项，然后点击「转换为 BMP」、「全部下载（ZIP）」按钮即可。支持拖放文件。加密的 PDF 选好后会先出现「打开密码」栏和「打开」按钮，输入密码点「打开」后再继续。In the PDF to BMP Converter: Set "Resolution", "Pages (empty = all)", then click "Convert to BMP", "Download all (ZIP)". Drag-and-drop files is supported. For an encrypted PDF, a Password field and an Open button appear after you choose it — enter the password and click Open first.

BMP 文件为什么这么大？Why are BMP files so large?

BMP 不压缩，每个像素占 3 字节：A4 页面在 150 DPI 下约 1240 × 1754 像素，约 6.5 MB；300 DPI 约 26 MB。只是在屏幕上看的话，选 PDF 转 PNG 或 JPG 会小得多。BMP is uncompressed at 3 bytes per pixel: an A4 page at 150 DPI is about 1240 × 1754 pixels, roughly 6.5 MB, and about 26 MB at 300 DPI. For on-screen use, PDF to PNG or JPG is far smaller.

BMP 里会记录 DPI 吗？Is the DPI stored in the BMP?

会。文件头写入了对应的像素/米分辨率（如 72 DPI = 2835 像素/米），排版和打印软件可以据此还原原始纸张尺寸。透明区域统一填充为白色，因为 24 位 BMP 没有透明通道。Yes. The header stores the matching pixels-per-metre value (72 DPI = 2835 px/m), so layout and print software can restore the paper size. Transparent areas are filled white because 24-bit BMP has no alpha channel.

分辨率（DPI）怎么选？Which resolution (DPI) should I pick?

72–96 DPI 适合在屏幕上查看或网页使用，150 DPI 是清晰度和体积的平衡点，200–300 DPI 适合打印或需要放大细节，600 DPI 文件会非常大。A4 页面在 150 DPI 下约为 1240×1754 像素。72–96 DPI suits screens and the web, 150 DPI balances clarity and size, 200–300 DPI is for printing or zooming in, and 600 DPI files are very large. An A4 page at 150 DPI is about 1240×1754 pixels.

中文和特殊字体能正确显示吗？Are Chinese and special fonts rendered correctly?

页面由 pdf.js 渲染，支持嵌入字体、中日韩文字（含 CMap）、透明度和 JPEG2000/JBIG2 图片；未嵌入字体的文件会用相近的标准字体替代，个别排版可能与原软件略有差异。Pages are rendered with pdf.js, which supports embedded fonts, CJK text (with CMaps), transparency and JPEG2000/JBIG2 images. Non-embedded fonts are substituted with similar standard fonts, so rare layouts may differ slightly.

加密的 PDF 可以处理吗？Can it handle password-protected PDFs?

可以。如果 PDF 需要打开密码，会提示你输入；只有权限限制（无打开密码）的文件会自动打开。输出文件不再带密码，如需加密请使用“PDF 加密”工具。Yes. If the PDF needs an open password you'll be asked for it; files with only permission restrictions open automatically. The output is not password-protected — use the Protect PDF tool if needed.

文件会上传到服务器吗？Are my files uploaded?

不会。PDF 在你的浏览器里用 pdf-lib / pdf.js 处理，文件不会离开你的设备，关闭页面后不留存任何数据。No. The PDF is processed in your browser with pdf-lib / pdf.js; files never leave your device and nothing is kept after you close the page.

「PDF 转 BMP」免费吗？需要注册吗？Is the PDF to BMP Converter free? Do I need an account?

「PDF 转 BMP」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 PDF to BMP Converter is completely free with no sign-up or install and works on phones and desktops; what you enter is processed only in your browser.