Merge Images Vertically

In raster graphics compositing, stacking multiple images vertically requires calculating cumulative vertical offsets across a unified 2D canvas buffer. The primary mathematical challenge stems from width discrepancies: if Screenshot A was captured on an iPhone 15 Pro (1179px wide) and Screenshot B was taken on a tablet (1620px wide), placing them together without normalization leaves an awkward, stepped layout with uneven margins.

Our engine implements automated Width Normalization with aspect-preserving scaling. Given a target master width $W_{\text{master}}$ (typically chosen as the maximum width among input assets $\max(W_i)$ or a user-defined width), each input image $i$ is scaled by an optical ratio $s_i = W_{\text{master}} / W_i$. The scaled height of each image becomes: $$H'_i = H_i \times \frac{W_{\text{master}}}{W_i}$$ Given an outer margin $\text{Padding}$ and an inter-image spacing $\text{Gutter}$, the total synthesized canvas width $W_{\text{total}}$ and height $H_{\text{total}}$ are calculated as: $$W_{\text{total}} = W_{\text{master}} + 2 \times \text{Padding}$$ $$H_{\text{total}} = 2 \times \text{Padding} + \sum_{i=1}^{N} H'_i + (N - 1) \times \text{Gutter}$$ For each sequential image $k \in [1, N]$, the vertical origin coordinate $Y_k$ is computed via cumulative offset summation: $Y_k = \text{Padding} + \sum_{j=1}^{k-1} (H'_j + \text{Gutter})$. This mathematical stacking ensures perfectly flush, parallel left and right margins throughout the entire vertical scroll with zero optical distortion.

Depending on the technical intent of your composite, our engine provides two distinct layout paradigms: 1. Proportional Rescaling (Scale-to-Match Width): Standard for chat logs, long website screenshots, and webtoons. All images are scaled to share the exact same horizontal pixel width while preserving their native optical aspect ratios. Because all frames align flush from left to right, the composite achieves a clean, unified scroll reminiscent of an uninterrupted mobile screen. 2. Canvas Centering: Essential when stacking diverse graphics—such as combining a wide promotional banner, a square product photo, and a tall technical diagram. Under this mode, images retain their native pixel dimensions. The canvas width matches the widest asset, and narrower images are centered horizontally along the X-axis: $$X_{\text{offset}} = \text{Padding} + \frac{W_{\text{master}} - W_i}{2}$$ The empty margin space to the left and right of the narrower image is filled with a clean background color (such as pure white, dark slate, or transparent alpha), preserving the original pixel integrity of each asset.

Vertical image stacking solves numerous documentation challenges across enterprise and creative sectors: 1. Legal Discovery & HR Documentation: In commercial litigation, employment disputes, and tenancy conflicts, smartphone text conversations (SMS, WhatsApp, Signal, Slack) represent critical evidentiary records. Presenting dozens of loose, unsequenced screenshot files invites confusion and skepticism. Stacking screenshots chronologically into a single continuous vertical record creates an uninterrupted, easily auditable narrative that judges, mediators, and HR investigators can review effortlessly. 2. Financial Expense Management & Tax Audits: Independent contractors and corporate accounting departments routinely manage dozens of paper receipts. Stacking receipts vertically onto a uniform white canvas organizes expense reports into compact, orderly files ready for archival conversion. 3. Webtoons & Digital Comic Publishing: Digital artists and manga illustrators assemble sequential panels into continuous vertical scrolling webtoons specifically optimized for touch-swipe reading on smartphones and webtoon platforms.

Stitching long vertical scrolls presents unique technical challenges regarding browser memory limits. While horizontal images rarely exceed standard monitor widths, a vertical composite of 15 high-resolution smartphone screenshots can easily exceed 25,000 pixels in vertical height. Modern browser rendering engines (V8, WebKit, Gecko) impose strict maximum dimension limits on HTML5 Canvas allocations (e.g. 16,384px or 32,768px depending on GPU hardware). Our engine intelligently monitors canvas allocation constraints. If an extreme stitch approaches GPU texture memory limits, the engine offers automatic output downsampling or guides users to export via lightweight vector-friendly formats (such as WebP or PDF) to ensure seamless rendering without browser crashes.

To craft courtroom-ready evidence or publication-grade webtoon panels, integrate Merge Images Vertically into an organized sequence across the 2run.tools suite: 1. Pre-Processing & Header Trimming with Crop Image: Crop off redundant smartphone status bars (battery percentage, clock, cellular signal) and bottom navigation bars to ensure conversation bubbles flow seamlessly from panel to panel. 2. Privacy Redaction with Blur Image: If chat logs or receipts contain sensitive personal identifiers (credit card numbers, home addresses, phone numbers), obscure them using Blur Image before stacking. 3. Vertical Stacking via Merge Images Vertically: Ingest your prepared screenshots, select 'Scale to Match Width', and configure divider spacing. 4. Framing & Annotations: Frame the composite with Add Border or highlight key sections with Add Text Watermark. 5. Archival Packaging: Convert the long vertical graphic into a universal, multi-page legal document using Image to PDF, or compress for messaging using Compress Image.