Merge pull request matplotlib#28904 from QuLogic/remove-16bit-limits

Agg: Remove 16-bit limits

Author: greglucas

doc/users/next_whats_new/increased_figure_limits.rst

@@ -0,0 +1,9 @@
+Increased Figure limits with Agg renderer
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Figures using the Agg renderer are now limited to 2**23 pixels in each
+direction, instead of 2**16. Additionally, bugs that caused artists to not
+render past 2**15 pixels horizontally have been fixed.
+
+Note that if you are using a GUI backend, it may have its own smaller limits
+(which may themselves depend on screen size.)

extern/agg24-svn/include/agg_rasterizer_cells_aa.h

@@ -325,8 +325,10 @@ namespace agg
 
         if(dx >= dx_limit || dx <= -dx_limit)
         {
-            int cx = (x1 + x2) >> 1;
-            int cy = (y1 + y2) >> 1;
+            // These are overflow safe versions of (x1 + x2) >> 1; divide each by 2
+            // first, then add 1 if both were odd.
+            int cx = (x1 >> 1) + (x2 >> 1) + ((x1 & 1) & (x2 & 1));
+            int cy = (y1 >> 1) + (y2 >> 1) + ((y1 & 1) & (y2 & 1));
             line(x1, y1, cx, cy);
             line(cx, cy, x2, y2);
             return;

lib/matplotlib/tests/test_agg.py

@@ -199,7 +199,7 @@ def process_image(self, padded_src, dpi):
 
 
 def test_too_large_image():
-    fig = plt.figure(figsize=(300, 1000))
+    fig = plt.figure(figsize=(300, 2**25))
     buff = io.BytesIO()
     with pytest.raises(ValueError):
         fig.savefig(buff)

src/_backend_agg.cpp

@@ -33,10 +33,10 @@ RendererAgg::RendererAgg(unsigned int width, unsigned int height, double dpi)
         throw std::range_error("dpi must be positive");
     }
 
-    if (width >= 1 << 16 || height >= 1 << 16) {
+    if (width >= 1 << 23 || height >= 1 << 23) {
         throw std::range_error(
             "Image size of " + std::to_string(width) + "x" + std::to_string(height) +
-            " pixels is too large. It must be less than 2^16 in each direction.");
+            " pixels is too large. It must be less than 2^23 in each direction.");
     }
 
     unsigned stride(width * 4);

src/_backend_agg.h

@@ -117,10 +117,10 @@ class RendererAgg
     typedef agg::renderer_scanline_bin_solid<renderer_base> renderer_bin;
     typedef agg::rasterizer_scanline_aa<agg::rasterizer_sl_clip_dbl> rasterizer;
 
-    typedef agg::scanline_p8 scanline_p8;
-    typedef agg::scanline_bin scanline_bin;
+    typedef agg::scanline32_p8 scanline_p8;
+    typedef agg::scanline32_bin scanline_bin;
     typedef agg::amask_no_clip_gray8 alpha_mask_type;
-    typedef agg::scanline_u8_am<alpha_mask_type> scanline_am;
+    typedef agg::scanline32_u8_am<alpha_mask_type> scanline_am;
 
     typedef agg::renderer_base<agg::pixfmt_gray8> renderer_base_alpha_mask_type;
     typedef agg::renderer_scanline_aa_solid<renderer_base_alpha_mask_type> renderer_alpha_mask_type;

src/_image_resample.h

@@ -712,6 +712,7 @@ void resample(
 
     using renderer_t = agg::renderer_base<output_pixfmt_t>;
     using rasterizer_t = agg::rasterizer_scanline_aa<agg::rasterizer_sl_clip_dbl>;
+    using scanline_t = agg::scanline32_u8;
 
     using reflect_t = agg::wrap_mode_reflect;
     using image_accessor_t = agg::image_accessor_wrap<input_pixfmt_t, reflect_t, reflect_t>;
@@ -739,7 +740,7 @@ void resample(
 
     span_alloc_t span_alloc;
     rasterizer_t rasterizer;
-    agg::scanline_u8 scanline;
+    scanline_t scanline;
 
     span_conv_alpha_t conv_alpha(params.alpha);