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thumbnailer: Simplify pixbuf scaling #107

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thumbnailer: Simplify pixbuf scaling #107

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34 changes: 5 additions & 29 deletions src/Services/Thumbnailer.vala
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Original file line number Diff line number Diff line change
Expand Up @@ -57,7 +57,7 @@ public class PaperClip.Services.Thumbnailer {
if (image_area >= max_area) {
debug ("Image is too big! Loading it in a reduced size");
retval = yield ThreadManager.run_in_thread<Gdk.Texture> (
() => load_scaled (surface, basename));
() => load_scaled (surface));
} else {
debug ("Loading image in its default size");
retval = yield ThreadManager.run_in_thread<Gdk.Texture> (() => load_memory (surface));
Expand All @@ -66,15 +66,9 @@ public class PaperClip.Services.Thumbnailer {
return retval;
}

private Gdk.Texture load_scaled (Cairo.ImageSurface surface, string basename) throws Error {
private Gdk.Texture load_scaled (Cairo.ImageSurface surface) throws Error {
float max_area = max_size * max_size * area_threshold;
int width = surface.get_width (), height = surface.get_height ();
string save_path = create_cache_file (basename);
Cairo.Status status = surface.write_to_png (save_path);

if (status != SUCCESS) {
throw new ThumbnailError.FAILED_EXPORT (@"Failed to export $save_path: $status");
}

float scale_factor = 0.1f;
for (; scale_factor < 0.8f; scale_factor+=0.1f) {
Expand All @@ -88,30 +82,12 @@ public class PaperClip.Services.Thumbnailer {
float scaled_height = height * scale_factor, scaled_width = width * scale_factor;
debug (@"Height: $height -> $scaled_height. Width: $width -> $scaled_width");

var pixbuf = new Gdk.Pixbuf.from_file_at_size (save_path, (int) scaled_width, (int) scaled_height);
var texture = Gdk.Texture.for_pixbuf (pixbuf);
var pixbuf = Gdk.pixbuf_get_from_surface (surface, 0, 0, width, height);
var scaled_pixbuf = pixbuf.scale_simple ((int) scaled_width, (int) scaled_height, Gdk.InterpType.BILINEAR);
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@Diego-Ivan Diego-Ivan Apr 16, 2025

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Unfortunately, GdkPixbuf's scaling provides a lower quality thumbnail. In the DocumentThumbnail widget we use either a Trilinear interpolation or a nearest interpolation. The latter is supported by GdkPixbuf but the former is not.

I also want to remove GdkPixbuf from the codebase in favor of Glycin since it plays better with GdkTextures and would allow us to remove this ugly scaling implementation I made.

Paper-Clip/src/DocumentThumbnail.vala

Lines 73 to 78 in 7777db7

Gsk.ScalingFilter filter = LINEAR;
if (scaled_width > thumbnail_texture.width || scaled_height > thumbnail_texture.height) {
filter = NEAREST;
} else {
filter = TRILINEAR;
}

var texture = Gdk.Texture.for_pixbuf (scaled_pixbuf);
return texture;
}

private string? create_cache_file (string basename) throws Error {
string destination_path = Path.build_path (Path.DIR_SEPARATOR_S,
Environment.get_tmp_dir (),
"thumbnails");
int result = DirUtils.create_with_parents (destination_path, 0777);
if (result < 0) {
throw new ThumbnailError.FAILED_TO_CACHE (@"Unable to create tmp path $destination_path");
}

string destination_file = Path.build_filename (destination_path,
"%s.png".printf (basename));

var file = File.new_for_path (destination_file);
if (!file.query_exists ()) {
file.create (NONE);
}
return destination_file;
}

private Gdk.Texture load_memory (Cairo.ImageSurface surface) throws Error {
int height = surface.get_height (), width = surface.get_width ();
size_t size = height * width * 4;
Expand Down