1 files changed, 16 insertions, 5 deletions
diff --git a/src/image.zig b/src/image.zig
index 936fe19a..3a3f1932 100644
--- a/src/image.zig
+++ b/src/image.zig
@@ -305,7 +305,6 @@ pub const GlyphArt = struct {
 
     pub fn render(gpa: std.mem.Allocator, rgba: []const u8, iw: usize, ih: usize, max_cols: usize, max_rows: usize, pal: Palette, ascii: bool) !Grid {
         if (iw == 0 or ih == 0 or max_cols == 0 or max_rows == 0) return .{ .cells = try gpa.alloc(Cell, 0), .cols = 0, .rows = 0 };
-        const gset: []const Glyph = if (ascii) &glyphs_ascii else &glyphs;
         // contain-fit; cells are ~twice as tall as wide, so a row spans 2 width-units.
         var cols = max_cols;
         var rows = (max_cols * ih) / (2 * iw);
@@ -315,16 +314,28 @@ pub const GlyphArt = struct {
         }
         cols = std.math.clamp(cols, 1, max_cols);
         rows = std.math.clamp(rows, 1, max_rows);
+        return renderRect(gpa, rgba, iw, ih, .{ .w = @intCast(iw), .h = @intCast(ih) }, cols, rows, pal, ascii);
+    }
 
+    /// The pixels of `src` (a rectangle of the `iw` x `ih` image) laid
+    /// over exactly `cols` x `rows` cells, whatever their shape: a
+    /// terminal's image fragment is already the size its cells are.
+    pub fn renderRect(gpa: std.mem.Allocator, rgba: []const u8, iw: usize, ih: usize, src: PixelRect, cols: usize, rows: usize, pal: Palette, ascii: bool) !Grid {
+        const x0: usize = @min(src.x, iw);
+        const y0: usize = @min(src.y, ih);
+        const sw: usize = @min(src.w, iw - x0);
+        const sh: usize = @min(src.h, ih - y0);
+        if (sw == 0 or sh == 0 or cols == 0 or rows == 0) return .{ .cells = try gpa.alloc(Cell, 0), .cols = 0, .rows = 0 };
+        const gset: []const Glyph = if (ascii) &glyphs_ascii else &glyphs;
         const cells = try gpa.alloc(Cell, cols * rows);
         var cy: usize = 0;
         while (cy < rows) : (cy += 1) {
-            const ry0 = cy * ih / rows;
-            const ry1 = @max(ry0 + 1, (cy + 1) * ih / rows);
+            const ry0 = y0 + cy * sh / rows;
+            const ry1 = @max(ry0 + 1, y0 + (cy + 1) * sh / rows);
             var cx: usize = 0;
             while (cx < cols) : (cx += 1) {
-                const rx0 = cx * iw / cols;
-                const rx1 = @max(rx0 + 1, (cx + 1) * iw / cols);
+                const rx0 = x0 + cx * sw / cols;
+                const rx1 = @max(rx0 + 1, x0 + (cx + 1) * sw / cols);
                 var cell: [64][3]u8 = undefined;
                 var sy: usize = 0;
                 while (sy < 8) : (sy += 1) {