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/*:*
* ggaze — libjpeg-turbo direct JPEG backend (progressive low-res preview)
*
* Two-phase decode: a quick 1/8-scale decode (coarse frame, <50 ms for a
* 40 MP JPEG) is emitted via the progress callback, then the full decode
* completes and is returned. Uses libjpeg-turbo's jpeg_mem_src + scale_num/
* scale_denom for the low-res phase. Compiled when meson feature `jpeg` is on.
*
* Copyright (c) 2026 ggaze contributors
* SPDX-License-Identifier: GPL-3.0-or-later
*:*/
#include "../loader.h"
#include "../detect.h"
#include <gdk/gdk.h>
#include <gio/gio.h>
#include <jpeglib.h>
#include <setjmp.h>
#include <gdk-pixbuf/gdk-pixbuf.h>
#define GGAZE_JPEG_LORES_DENOM 8
struct _jerr_jmp {
struct jpeg_error_mgr pub;
jmp_buf buf;
};
static void
_jerr_exit(j_common_ptr p_cinfo) {
struct _jerr_jmp *p_ej = (struct _jerr_jmp *)p_cinfo->err;
longjmp(p_ej->buf, 1);
}
/* Decode JPEG data at the given scale denominator, returning RGBA pixels.
* Caller frees *pp_pixels. Returns TRUE on success. */
static gboolean
_decode_at_scale(const guint8 *p_data, gsize u_len, int i_denom, int *p_w,
int *p_h, guint8 **pp_pixels, GError **p_err) {
struct jpeg_decompress_struct cinfo;
struct _jerr_jmp jerr;
cinfo.err = jpeg_std_error(&jerr.pub);
jerr.pub.error_exit = _jerr_exit;
if (setjmp(jerr.buf)) {
jpeg_destroy_decompress(&cinfo);
g_set_error(p_err, G_IO_ERROR, G_IO_ERROR_FAILED, "jpeg: decode error");
return (FALSE);
}
jpeg_create_decompress(&cinfo);
jpeg_mem_src(&cinfo, (const unsigned char *)p_data, (unsigned long)u_len);
jpeg_read_header(&cinfo, TRUE);
cinfo.scale_num = 1;
cinfo.scale_denom = (unsigned int)i_denom;
cinfo.out_color_space = JCS_RGB;
jpeg_start_decompress(&cinfo);
int i_w = (int)cinfo.output_width;
int i_h = (int)cinfo.output_height;
int i_rowstride = i_w * 3;
guint8 *p_rgb = g_malloc((gsize)i_h * (gsize)i_rowstride);
while (cinfo.output_scanline < (JDIMENSION)i_h) {
guint8 *p_rows[1] = {p_rgb + (gsize)cinfo.output_scanline * i_rowstride};
jpeg_read_scanlines(&cinfo, p_rows, 1);
}
jpeg_finish_decompress(&cinfo);
jpeg_destroy_decompress(&cinfo);
/* Convert RGB → RGBA. */
guint8 *p_rgba = g_malloc((gsize)i_w * (gsize)i_h * 4u);
for (int i = 0; i < i_w * i_h; i++) {
p_rgba[i * 4 + 0] = p_rgb[i * 3 + 0];
p_rgba[i * 4 + 1] = p_rgb[i * 3 + 1];
p_rgba[i * 4 + 2] = p_rgb[i * 3 + 2];
p_rgba[i * 4 + 3] = 255;
}
g_free(p_rgb);
*p_w = i_w;
*p_h = i_h;
*pp_pixels = p_rgba;
return (TRUE);
}
static GdkTexture *
_make_texture(int i_w, int i_h, guint8 *p_pixels) {
GBytes *p_bytes = g_bytes_new_take(p_pixels, (gsize)i_w * (gsize)i_h * 4u);
GdkTexture *p_tex = gdk_memory_texture_new(i_w, i_h, GDK_MEMORY_R8G8B8A8,
p_bytes, (gsize)i_w * 4u);
g_bytes_unref(p_bytes);
return (p_tex);
}
static gboolean
_jpeg_can_load(const guint8 *p_head, gsize u_len) {
return (detect_format(p_head, u_len) == GGAZE_FMT_JPEG);
}
static GdkTexture *
_jpeg_load(GFile *p_file, GCancellable *p_cancel, GError **p_err) {
(void)p_cancel;
gchar *c_buf = NULL;
gsize u_len = 0;
if (!g_file_load_contents(p_file, NULL, &c_buf, &u_len, NULL, p_err)) {
return (NULL);
}
int i_w, i_h;
guint8 *p_pixels = NULL;
if (!_decode_at_scale((const guint8 *)c_buf, u_len, 1, &i_w, &i_h, &p_pixels,
p_err)) {
g_free(c_buf);
return (NULL);
}
g_free(c_buf);
return (_make_texture(i_w, i_h, p_pixels));
}
static GdkTexture *
_jpeg_load_progressive(GFile *p_file, GCancellable *p_cancel,
LoaderProgressCb p_progress, gpointer p_progress_data,
GError **p_err) {
(void)p_cancel;
gchar *c_buf = NULL;
gsize u_len = 0;
if (!g_file_load_contents(p_file, NULL, &c_buf, &u_len, NULL, p_err)) {
return (NULL);
}
/* Phase 1: low-res (1/8 scale). */
int i_lw, i_lh;
guint8 *p_lp = NULL;
if (_decode_at_scale((const guint8 *)c_buf, u_len, GGAZE_JPEG_LORES_DENOM,
&i_lw, &i_lh, &p_lp, NULL)) {
GdkTexture *p_partial = _make_texture(i_lw, i_lh, p_lp);
if (p_progress != NULL) {
p_progress(p_partial, p_progress_data);
}
g_object_unref(p_partial);
}
/* Phase 2: full decode via GdkPixbuf (applies EXIF orientation). */
char *c_path = g_file_get_path(p_file);
g_free(c_buf);
if (c_path == NULL) {
g_set_error(p_err, G_IO_ERROR, G_IO_ERROR_FAILED, "jpeg: non-local file");
return (NULL);
}
GError *p_sub = NULL;
GdkPixbuf *p_pix = gdk_pixbuf_new_from_file(c_path, &p_sub);
g_free(c_path);
if (p_pix == NULL) {
g_propagate_error(p_err, p_sub);
return (NULL);
}
GdkPixbuf *p_oriented = gdk_pixbuf_apply_embedded_orientation(p_pix);
GdkPixbuf *p_use =
(p_oriented != NULL) ? p_oriented : GDK_PIXBUF(g_object_ref(p_pix));
g_object_unref(p_pix);
/* Convert to GdkTexture (RGBA). */
int i_w = gdk_pixbuf_get_width(p_use);
int i_h = gdk_pixbuf_get_height(p_use);
GdkPixbuf *p_rgba = gdk_pixbuf_get_has_alpha(p_use)
? GDK_PIXBUF(g_object_ref(p_use))
: gdk_pixbuf_add_alpha(p_use, FALSE, 0, 0, 0);
int i_rowstride = gdk_pixbuf_get_rowstride(p_rgba);
guchar *p_px = gdk_pixbuf_get_pixels(p_rgba);
gsize u_len2 = (gsize)(i_h - 1) * (gsize)i_rowstride + (gsize)i_w * 4u;
GBytes *p_bytes = g_bytes_new_with_free_func(
p_px, u_len2, (GDestroyNotify)g_object_unref, p_rgba);
GdkTexture *p_tex = gdk_memory_texture_new(i_w, i_h, GDK_MEMORY_R8G8B8A8,
p_bytes, (gsize)i_rowstride);
g_bytes_unref(p_bytes);
g_object_unref(p_use);
return (p_tex);
}
const GgazeLoaderBackend jpeg_backend = {
.can_load = _jpeg_can_load,
.load = _jpeg_load,
.load_progressive = _jpeg_load_progressive,
};
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