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Fix #347: Faster text rendering in Agg #5361

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Merged
merged 2 commits into from
Nov 5, 2015
Merged

Fix #347: Faster text rendering in Agg #5361

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340c256
Fix #347: Faster text rendering in Agg
mdboom Oct 30, 2015
83a1025
Use blend_color_solid as suggested by @jkseppan
mdboom Nov 2, 2015
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Fix #347: Faster text rendering in Agg 
When the text isn't rotated, we can skip a lot of machinery by just
doing a direct blending of text pixels onto the output buffer.
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@mdboom
mdboom committed Nov 2, 2015
commit 340c25623bfd3f601bc8b13825467e463135ca3c
5 changes: 5 additions & 0 deletions 5 doc/users/whats_new/faster-text-rendering.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,5 @@
Faster text rendering
---------------------

Rendering text in the Agg backend is now less fuzzy and about 20%
faster to draw.
95 changes: 61 additions & 34 deletions 95 src/_backend_agg.h
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Expand Up @@ -734,41 +734,68 @@ inline void RendererAgg::draw_text_image(GCAgg &gc, ImageArray &image, int x, in
typedef agg::renderer_scanline_aa<renderer_base, color_span_alloc_type, span_gen_type>
renderer_type;

theRasterizer.reset_clipping();
rendererBase.reset_clipping(true);
set_clipbox(gc.cliprect, theRasterizer);
if (angle != 0.0) {
agg::rendering_buffer srcbuf(
image.data(), (unsigned)image.dim(1),
(unsigned)image.dim(0), (unsigned)image.dim(1));
agg::pixfmt_gray8 pixf_img(srcbuf);

theRasterizer.reset_clipping();
rendererBase.reset_clipping(true);
set_clipbox(gc.cliprect, theRasterizer);

agg::trans_affine mtx;
mtx *= agg::trans_affine_translation(0, -image.dim(0));
mtx *= agg::trans_affine_rotation(-angle * agg::pi / 180.0);
mtx *= agg::trans_affine_translation(x, y);

agg::path_storage rect;
rect.move_to(0, 0);
rect.line_to(image.dim(1), 0);
rect.line_to(image.dim(1), image.dim(0));
rect.line_to(0, image.dim(0));
rect.line_to(0, 0);
agg::conv_transform<agg::path_storage> rect2(rect, mtx);

agg::trans_affine inv_mtx(mtx);
inv_mtx.invert();

agg::image_filter_lut filter;
filter.calculate(agg::image_filter_spline36());
interpolator_type interpolator(inv_mtx);
color_span_alloc_type sa;
image_accessor_type ia(pixf_img, agg::gray8(0));
image_span_gen_type image_span_generator(ia, interpolator, filter);
span_gen_type output_span_generator(&image_span_generator, gc.color);
renderer_type ri(rendererBase, sa, output_span_generator);

theRasterizer.add_path(rect2);
agg::render_scanlines(theRasterizer, slineP8, ri);
} else {
agg::rect_i fig, text;

fig.init(0, 0, width, height);
text.init(x, y - image.dim(0), x + image.dim(1), y);
text.clip(fig);

if (gc.cliprect.x1 != 0.0 || gc.cliprect.y1 != 0.0 || gc.cliprect.x2 != 0.0 || gc.cliprect.y2 != 0.0) {
agg::rect_i clip;

clip.init(int(mpl_round(gc.cliprect.x1)),
int(mpl_round(gc.cliprect.y1)),
int(mpl_round(gc.cliprect.x2)),
int(mpl_round(gc.cliprect.y2)));
text.clip(clip);
}

agg::rendering_buffer srcbuf(
image.data(), (unsigned)image.dim(1), (unsigned)image.dim(0), (unsigned)image.dim(1));
agg::pixfmt_gray8 pixf_img(srcbuf);

agg::trans_affine mtx;
mtx *= agg::trans_affine_translation(0, -image.dim(0));
mtx *= agg::trans_affine_rotation(-angle * agg::pi / 180.0);
mtx *= agg::trans_affine_translation(x, y);

agg::path_storage rect;
rect.move_to(0, 0);
rect.line_to(image.dim(1), 0);
rect.line_to(image.dim(1), image.dim(0));
rect.line_to(0, image.dim(0));
rect.line_to(0, 0);
agg::conv_transform<agg::path_storage> rect2(rect, mtx);

agg::trans_affine inv_mtx(mtx);
inv_mtx.invert();

agg::image_filter_lut filter;
filter.calculate(agg::image_filter_spline36());
interpolator_type interpolator(inv_mtx);
color_span_alloc_type sa;
image_accessor_type ia(pixf_img, agg::gray8(0));
image_span_gen_type image_span_generator(ia, interpolator, filter);
span_gen_type output_span_generator(&image_span_generator, gc.color);
renderer_type ri(rendererBase, sa, output_span_generator);

theRasterizer.add_path(rect2);
agg::render_scanlines(theRasterizer, slineP8, ri);
for (int yi = text.y1; yi < text.y2; ++yi) {
for (int xi = text.x1; xi < text.x2; ++xi) {
typename ImageArray::value_type pixel = image(
yi - (y - image.dim(0)), xi - x);
pixFmt.blend_pixel(xi, yi, gc.color, pixel);
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I'm not an agg expert, but it seems that blend_color_hspan could be even faster.

http://sourceforge.net/p/vector-agg/mailman/message/5116797/

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I'll play with that. blend_color_hspan doesn't take as inputs exactly the same thing that we have, so there may be overhead in creating that first negating any wins. Only benchmarking will tell.

}
}
}
}

class span_conv_alpha
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