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Qrencode: Break out upsampling into a separate function

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This commit is contained in:
mjk 2022-02-25 22:43:02 +00:00
parent 855a98c045
commit d3ae541673
1 changed files with 35 additions and 16 deletions
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51
plugins/omemo/vapi/libqrencode.vapi
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@ -38,26 +38,45 @@ namespace Qrencode {
public Pixbuf to_pixbuf(int module_size) {
GLib.assert(module_size > 0);
var src_w = width;
var src = data[0:width*width];
var dst_w = src_w*module_size;
var dst = new uint8[dst_w*dst_w*3];
for (int src_y = 0; src_y < src_w; src_y++) {
for (int repeat_y = 0; repeat_y < module_size; repeat_y++) {
var dst_y = src_y*module_size + repeat_y;
for (int src_x = 0; src_x < src_w; src_x++) {
uint8 color = (src[src_y*src_w + src_x] & 1) == 1 ? 0 : 255;
for (int repeat_x = 0; repeat_x < module_size; repeat_x++) {
var dst_x = src_x*module_size + repeat_x;
var px_idx = dst_y*dst_w + dst_x;
dst[px_idx*3+0] = color;
dst[px_idx*3+1] = color;
dst[px_idx*3+2] = color;
var dst_width = width*module_size;
var dst_data = new uint8[dst_width*dst_width*3];
expand_and_upsample(data,width,width, dst_data,dst_width,dst_width);
return new Pixbuf.from_data(dst_data,
Colorspace.RGB, false, 8, dst_width, dst_width, dst_width*3);
}
/** Does 2D nearest-neighbor upsampling of an array of single-byte
* samples, while expanding the least significant bit of each sample
* to three 0-or-255 bytes.
*/
private void expand_and_upsample(
uint8[] src, uint src_w, uint src_h,
uint8[] dst, uint dst_w, uint dst_h) {
GLib.assert(dst_w % src_w == 0);
GLib.assert(dst_h % src_h == 0);
var scale_x = dst_w/src_w,
scale_y = dst_h/src_h;
/* Doing the iteration in the order of destination samples for
* improved cache-friendliness (dst is 48 times larger than src in
* the typical case of scaling by 4x4).
* The choice of multiple nested loops over a single one is for
* avoiding a ton of divisions by non-constants.
*/
for (uint src_y = 0; src_y < src_h; ++src_y) {
for (uint repeat_y = 0; repeat_y < scale_y; ++repeat_y) {
var dst_y = src_y*scale_y + repeat_y;
for (uint src_x = 0; src_x < src_w; ++src_x) {
uint8 value = (src[src_y*src_w + src_x] & 1)==1 ? 0:255;
for (uint repeat_x = 0; repeat_x < scale_x; ++repeat_x){
var dst_x = src_x*scale_x + repeat_x;
var dst_idx = dst_y*dst_w + dst_x;
dst[dst_idx*3+0] = value;
dst[dst_idx*3+1] = value;
dst[dst_idx*3+2] = value;
}
}
}
}
return new Pixbuf.from_data(dst, Colorspace.RGB, false, 8, dst_w, dst_w, dst_w*3);
}
}
}