From a phone photo to exact print pixels
Pick a photo straight from your device and it is decoded into an in-memory canvas on this page — the image is processed only in your browser and is never uploaded, so there is nothing to sign up for and nothing to delete afterwards. Choose a target poster size from 8×10, 11×14, 16×20, 18×24 and 24×36 inches plus A4 and A3, and the export canvas is built at an exact 300 dots per inch: the 18×24 preset becomes 5400×7200 pixels, 24×36 becomes 7200×10800, and the metric sizes use the precise 2.54 conversion. The output dimensions in the result panel update before you export, so you always know how large the PNG will actually be.
Two fitting modes solve the two different problems photographers meet. Fit Crop scales the picture until it completely fills the poster rectangle and removes the overflow, exactly like a photo lab's centre crop; the crop focus sliders move the kept centre point vertically and horizontally, and clicking anywhere in the preview resets that point, so faces, horizons or buildings stay inside the frame when aspect ratios differ. Fit Contain keeps every pixel visible and pads the empty band instead — a letterbox you can colour with the picker or one of the midnight, black, white, warm-white and gold presets — making mixed-orientation photos print cleanly with no chopped edges.
Stepwise downsampling for a clean PNG
Shrinking a twelve-megapixel photo straight into a print buffer can shimmer along edges, because a single drawImage pass has to discard several source pixels for every output pixel. The export instead reduces the image in controlled half-size steps through intermediate canvases until it is close to the target, with high-quality smoothing enabled for the final fractional draw, which keeps text, skyline lines and portrait outlines crisp at the edges. The composited result is encoded locally as a PNG named with the format and pixel dimensions as a suffix, the result panel shows the real encoded file size, and Download writes that file to disk — no watermark, no server round trip, and no copy left behind when you close the tab.
从手机照片到精确的印刷像素
直接从设备选择照片，它会在本页被解码进一块内存 canvas——图片只在你的浏览器里处理，绝不上传，因此无需注册，用完也无需删除任何记录。目标海报尺寸可选 8×10、11×14、16×20、18×24、24×36 英寸以及 A4、A3；导出画布按精确的每英寸 300 点构建：18×24 预设对应 5400×7200 像素，24×36 对应 7200×10800，公制尺寸使用精确的 2.54 换算。结果面板会在导出前实时显示输出像素数，让你提前知道 PNG 的实际规模。
两种适配模式分别解决摄影师常遇到的两类问题。Fit Crop 会把图片放大到完全填满海报矩形并裁掉溢出部分，与洗印店的居中裁剪完全一致；裁剪焦点滑块可纵向、横向移动保留的中心点，点击预览任意位置也能重设中心点，让比例不同的照片依旧保住人脸、地平线或建筑。Fit Contain 则保留全部像素，用空白边距补齐——边距颜色可用取色器自由调配，或直接选深夜蓝、黑、白、暖白、金五个预设——让横竖不一的照片也能干净印刷，不切掉任何边缘。
分步降采样，导出干净 PNG
把上千万像素的照片一次性缩到打印缓冲区，边缘容易出现闪烁，因为单次 drawImage 要为每个输出像素丢弃数个源像素。导出时改为通过中间画布以可控的一半尺寸逐级缩小，直到接近目标，最后一次非整数缩放开启高质量平滑，让文字、天际线轮廓与人物边缘保持锐利。合成结果在本地编码为 PNG，文件名自带尺寸与像素后缀，结果面板显示真实编码后的文件大小；点击下载即写入磁盘——无水印、无服务器往返，关闭标签页后不留下任何副本。
Fit Crop or Fit Contain — which one should I use?
Fit Crop fills the whole poster edge to edge and is the classic full-bleed photo print; move the focus point if your subject is off-centre. Fit Contain shows the entire image with colour bars top and bottom or left and right; choose it when cropping anything off is unacceptable, such as a scanned document or a group photo.
Fit Crop 和 Fit Contain 应该选哪个？
Fit Crop 会让照片铺满整张海报，是经典的满版洗印效果；主体偏离中心时移动裁剪焦点即可。Fit Contain 会完整显示整张图片，以上下或左右的彩色边距补齐；扫描件、集体合影等任何边缘都不能裁切时选它。
Why downsample in half-size steps instead of one resize?
When several source pixels collapse into one output pixel in a single pass, fine detail aliases into jagged edges. Repeated half-scale reductions average neighbours at every stage, and the final high-quality draw only handles a small ratio — visibly cleaner diagonal lines and smoother gradients in the 300 DPI print.
为什么要逐级减半缩小，而不是一次缩放？
多个源像素在单趟处理中坍缩为一个输出像素时，细节会形成锯齿。逐级减半会在每一级平均相邻像素，最后的高质量绘制只需处理很小的比例——300 DPI 印刷品中的斜线明显更干净、渐变更平滑。
Is my photo uploaded anywhere, and why PNG instead of JPG?
No upload happens at all — the file is read locally, composited in canvas and exported from the same tab, so refreshing releases it. PNG was chosen because it is lossless, keeps resampled edges free of compression blocks and supports flat letterbox colours cleanly; for very large prints it is also the format most labs accept without re-encoding.
照片会被上传吗？为什么导出 PNG 而不是 JPG？
全程没有任何上传——文件在本地读取、在 canvas 合成、从同一标签页导出，刷新即释放。选择 PNG 是因为它无损，重采样后的边缘不会产生压缩块，纯色边距也干净；对于超大尺寸印刷，它也是大多数印厂无需再次编码即可接受的格式。
