Zach's git repos / ccharter-c
efficient program to spit out SVG for guitar/uke chord frett diagram
Diffstat (limited to 'ccharter.c')
-rw-r--r--ccharter.c103
1 files changed, 103 insertions, 0 deletions
diff --git a/ccharter.c b/ccharter.c
new file mode 100644
index 0000000..fdd895e
--- /dev/null
+++ b/ccharter.c
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+var ChordCharter = {
+
+ drawChord: function (canvasId, originX, originY, chordName, chordFrets) {
+
+ var chord = {
+ name: chordName,
+ frets: chordFrets
+ };
+
+ fretsCount = chord.frets.length;
+
+ var c=document.getElementById(canvasId);
+ var ctx=c.getContext("2d");
+ ctx.fillStyle="#000";
+
+ var origin = { x: originX, y: originY };
+ var props = { width: 50, height: 60 };
+
+ // Reset previous path that may have been created.
+ ctx.beginPath();
+
+ // horizontals
+
+ for (counter in new Array(0, 1, 2, 3, 4)) {
+ ctx.moveTo(origin.x - 1, origin.y + (counter * props.height / 4));
+ ctx.lineTo(origin.x + props.width + 1, origin.y + (counter * props.height / 4));
+ ctx.stroke();
+ }
+
+ // verts
+ for ( i = 0; i < fretsCount; i++ ) {
+ ctx.moveTo(origin.x + (i * props.width / (fretsCount - 1)), origin.y);
+ ctx.lineTo(origin.x + (i * props.width / (fretsCount - 1)), origin.y + props.height);
+ ctx.stroke();
+ }
+
+ ctx.stroke();
+
+ // label
+
+ ctx.font = "bold 10pt Verdana";
+ ctx.textAlign = "center";
+ ctx.fillText(chord.name, origin.x + props.width / 2, origin.y - 5);
+ ctx.font = "7pt Verdana";
+
+ // If any dots are after 4, adjust the root to be the lowest non-zero fret
+ // If the root is zero , thicken the top fret
+
+ var baseFret = 0;
+ var adjBaseFret = false;
+ var lowestFret = 0;
+
+ for (j=0; j < chord.frets.length; j++) {
+ if (chord.frets.charAt(j) != 'x' && chord.frets.charAt(j) != 'X' && chord.frets.charAt(j) > 0) {
+ if (chord.frets.charAt(j) < lowestFret || lowestFret == 0) {
+ lowestFret = chord.frets.charAt(j);
+ }
+ if (chord.frets.charAt(j) > 4) {
+ adjBaseFret = true;
+ }
+ }
+ }
+
+ if (adjBaseFret) {
+ baseFret = lowestFret - 1;
+ }
+
+ // dots
+
+ var dotsize = 3.5;
+
+ var i = 0;
+
+ for (j=0; j < chord.frets.length; j++) {
+
+ ctx.alignText = "left";
+ ctx.fillText(chord.frets.charAt(j), origin.x + (i * props.width / (fretsCount - 1)), origin.y + props.height + 12);
+
+ if (chord.frets.charAt(j) == 0) {
+
+
+ } else if (chord.frets.charAt(j) == 'x' || chord.frets.charAt(j) == 'X') {
+
+ } else {
+ ctx.beginPath();
+ ctx.arc(origin.x + (i * props.width / (fretsCount -1)), origin.y - 7.5 + (15 * (chord.frets.charAt(j) - baseFret)), dotsize, 0, Math.PI*2,true);
+ ctx.closePath();
+ ctx.fill();
+ }
+ i++;
+ }
+
+ // base fret indicator
+
+ if (baseFret > 0) {
+ ctx.alignText = "left";
+ ctx.fillText(baseFret + 1, origin.x - 10, origin.y + 11);
+ } else {
+ ctx.alignText = "left";
+ ctx.fillText("3", origin.x - 10, origin.y + 41);
+ }
+ }
+};