Short video cover splitter
Split a long image into the panels a Douyin/TikTok profile cover needs, giving exact crop rectangles and upload order, with an optional 3:4 fit to avoid stretching.
Runs in your browserEvery computation happens in your browser — your data never leaves this device.
Crop plan
Crop rectangle per panel plus the upload order.
Enter the source size to calculate
Source width: 0 · Source height: 0 · Panels: 0 · Base panel width: 0
What this tool does
- Build a three-panel profile cover: split the long image, crop each panel with the printed x/y/width/height and upload them in order.
- Avoid stretching: enable the ratio fit and crop to 3:4 so the profile preview is not squashed.
- Batch production: feed the crop rectangles to Canvas or ImageMagick and generate a whole set at once.
- Verify dimensions: the width check line shows whether the panel widths sum to the source width, catching pixel loss such as 1079.
Example
Input
1080x1920
Output
源图尺寸：1080 × 1920 像素 切成 3 格：每格宽 360 像素（余数 0 分给最左边几格） 宽度校验：360 + 360 + 360 = 1080 各格裁剪矩形（按此顺序上传）： 第 1 格：x=0 y=720 w=360 h=480 中心 (180, 960) 第 2 格：x=360 y=720 w=360 h=480 中心 (540, 960) 第 3 格：x=720 y=720 w=360 h=480 中心 (900, 960) 等比填充：每格按 3:4 居中裁切，避免主页预览被拉伸变形。 封面总像素：2073600（2.07 MP）
Panel width is ⌊width ÷ panels⌋ with the remainder handed to the leftmost panels, so no pixel is lost.
Frequently asked questions
Why not just divide the width by the panel count?
Because it does not always divide evenly. 1080 ÷ 3 is exactly 360, but 1000 ÷ 3 is 333.33 and rounding down loses a pixel. The tool computes base = ⌊width ÷ panels⌋ and hands the remainder to the leftmost panels, so 1000 in three panels becomes 334 + 333 + 333 = 1000, echoed in the width check line.
What does the ratio fit do?
Each profile panel is displayed at a fixed aspect (3:4 is common). Cropping at full height lets the platform stretch the image. With the fit enabled the tool centres a rectangle of the target ratio inside each panel — for 1080×1920 in three panels at 3:4 that is a centred 360×480 region — so nothing distorts.
How many panels are supported?
One to six, with three as the default (the common Douyin/TikTok profile mosaic). More than six raises an error, because each panel would be unreadably small on a phone.
How do I use the crop rectangles?
x and y are the top-left corner and w and h the size, all in pixels. In Canvas use ctx.drawImage(img, x, y, w, h, 0, 0, w, h); on the command line use magick input.png -crop WxH+X+Y out.png. The mapping is one to one.
How is the source size written?
As widthxheight, for example 1080x1920; × and commas are also accepted. Dimensions must be between 30 and 20000 pixels, and anything outside that range errors instead of producing a meaningless cover.
Are my images uploaded?
No. The tool only computes geometry and prints crop coordinates; the actual cutting happens in your local canvas or script and the image never leaves the device.
Keywords：短视频封面封面分割抖音封面TikTok封面主页拼图image split裁剪矩形