[PATCH v2] Added parameter to take screenshot with screendump as PNG

[Kshitij Suri]

Currently screendump only supports PPM format, which is un-compressed and not
standard. Added a "format" parameter to qemu monitor screendump capabilites
to support PNG image capture using libpng. The param was added in QAPI schema
of screendump present in ui.json along with png_save() function which converts
pixman_image to PNG. HMP command equivalent was also modified to support the
feature.

Example usage:
{ "execute": "screendump", "arguments": { "filename": "/tmp/image", 
"format":"png" } }

Resolves: https://gitlab.com/qemu-project/qemu/-/issues/718

Signed-off-by: Kshitij Suri <kshitij.suri@nutanix.com>
---
diff to v1:
  - Removed repeated alpha conversion operation.
  - Modified logic to mirror png conversion in vnc-enc-tight.c file.
  - Added a new CONFIG_PNG parameter for libpng support.
  - Changed input format to enum instead of string.

 hmp-commands.hx    | 11 +++---
 meson.build        | 13 +++++--
 meson_options.txt  |  2 +
 monitor/hmp-cmds.c |  8 +++-
 qapi/ui.json       | 24 ++++++++++--
 ui/console.c       | 97 ++++++++++++++++++++++++++++++++++++++++++++--
 6 files changed, 139 insertions(+), 16 deletions(-)

diff --git a/hmp-commands.hx b/hmp-commands.hx
index 70a9136ac2..e43c9954b5 100644
--- a/hmp-commands.hx
+++ b/hmp-commands.hx
@@ -244,17 +244,18 @@ ERST
 
     {
         .name       = "screendump",
-        .args_type  = "filename:F,device:s?,head:i?",
-        .params     = "filename [device [head]]",
-        .help       = "save screen from head 'head' of display device 'device' 
"
-                      "into PPM image 'filename'",
+        .args_type  = "filename:F,device:s?,head:i?,format:f?",
+        .params     = "filename [device [head]] [format]",
+        .help       = "save screen from head 'head' of display device 'device'"
+                      "in specified format 'format' as image 'filename'."
+                      "Currently only 'png' and 'ppm' formats are supported.",
         .cmd        = hmp_screendump,
         .coroutine  = true,
     },
 
 SRST
 ``screendump`` *filename*
-  Save screen into PPM image *filename*.
+  Save screen as an image *filename*.
 ERST
 
     {
diff --git a/meson.build b/meson.build
index 8df40bfac4..fd550c01ec 100644
--- a/meson.build
+++ b/meson.build
@@ -1112,13 +1112,16 @@ if gtkx11.found()
   x11 = dependency('x11', method: 'pkg-config', required: gtkx11.found(),
                    kwargs: static_kwargs)
 endif
-vnc = not_found
 png = not_found
+png = dependency('libpng', required: get_option('png'),
+                   method: 'pkg-config', kwargs: static_kwargs)
+vnc = not_found
+vnc_png = not_found
 jpeg = not_found
 sasl = not_found
 if get_option('vnc').allowed() and have_system
   vnc = declare_dependency() # dummy dependency
-  png = dependency('libpng', required: get_option('vnc_png'),
+  vnc_png = dependency('libpng', required: get_option('vnc_png'),
                    method: 'pkg-config', kwargs: static_kwargs)
   jpeg = dependency('libjpeg', required: get_option('vnc_jpeg'),
                     method: 'pkg-config', kwargs: static_kwargs)
@@ -1537,9 +1540,10 @@ config_host_data.set('CONFIG_TPM', have_tpm)
 config_host_data.set('CONFIG_USB_LIBUSB', libusb.found())
 config_host_data.set('CONFIG_VDE', vde.found())
 config_host_data.set('CONFIG_VHOST_USER_BLK_SERVER', 
have_vhost_user_blk_server)
+config_host_data.set('CONFIG_PNG', png.found())
 config_host_data.set('CONFIG_VNC', vnc.found())
 config_host_data.set('CONFIG_VNC_JPEG', jpeg.found())
-config_host_data.set('CONFIG_VNC_PNG', png.found())
+config_host_data.set('CONFIG_VNC_PNG', vnc_png.found())
 config_host_data.set('CONFIG_VNC_SASL', sasl.found())
 config_host_data.set('CONFIG_VIRTFS', have_virtfs)
 config_host_data.set('CONFIG_VTE', vte.found())
@@ -3579,11 +3583,12 @@ summary_info += {'curses support':    curses}
 summary_info += {'virgl support':     virgl}
 summary_info += {'curl support':      curl}
 summary_info += {'Multipath support': mpathpersist}
+summary_info += {'PNG support':       png}
 summary_info += {'VNC support':       vnc}
 if vnc.found()
   summary_info += {'VNC SASL support':  sasl}
   summary_info += {'VNC JPEG support':  jpeg}
-  summary_info += {'VNC PNG support':   png}
+  summary_info += {'VNC PNG support':   vnc_png}
 endif
 if targetos not in ['darwin', 'haiku', 'windows']
   summary_info += {'OSS support':     oss}
diff --git a/meson_options.txt b/meson_options.txt
index 52b11cead4..88148dec6c 100644
--- a/meson_options.txt
+++ b/meson_options.txt
@@ -177,6 +177,8 @@ option('vde', type : 'feature', value : 'auto',
        description: 'vde network backend support')
 option('virglrenderer', type : 'feature', value : 'auto',
        description: 'virgl rendering support')
+option('png', type : 'feature', value : 'auto',
+       description: 'PNG support with libpng')
 option('vnc', type : 'feature', value : 'auto',
        description: 'VNC server')
 option('vnc_jpeg', type : 'feature', value : 'auto',
diff --git a/monitor/hmp-cmds.c b/monitor/hmp-cmds.c
index 8c384dc1b2..c300545f34 100644
--- a/monitor/hmp-cmds.c
+++ b/monitor/hmp-cmds.c
@@ -1677,9 +1677,15 @@ hmp_screendump(Monitor *mon, const QDict *qdict)
     const char *filename = qdict_get_str(qdict, "filename");
     const char *id = qdict_get_try_str(qdict, "device");
     int64_t head = qdict_get_try_int(qdict, "head", 0);
+    const char *input_format  = qdict_get_str(qdict, "format");
     Error *err = NULL;
+    ImageFormat format = IMAGE_FORMAT_PPM;
+    if (input_format != NULL && strcmp(input_format, "png") == 0) {
+        format = IMAGE_FORMAT_PNG;
+    }
 
-    qmp_screendump(filename, id != NULL, id, id != NULL, head, &err);
+    qmp_screendump(filename, id != NULL, id, id != NULL, head,
+                   input_format != NULL, format, &err);
     hmp_handle_error(mon, err);
 }
 
diff --git a/qapi/ui.json b/qapi/ui.json
index 9354f4c467..8caeb2d3bb 100644
--- a/qapi/ui.json
+++ b/qapi/ui.json
@@ -73,12 +73,27 @@
 ##
 { 'command': 'expire_password', 'data': {'protocol': 'str', 'time': 'str'} }
 
+##
+# @ImageFormat:
+#
+# Available list of supported types.
+#
+# @png: PNG format
+#
+# @ppm: PPM format
+#
+# Since: 6.3
+#
+##
+{ 'enum': 'ImageFormat',
+  'data': ['ppm', 'png'] }
+
 ##
 # @screendump:
 #
-# Write a PPM of the VGA screen to a file.
+# Write a screenshot of the VGA screen to a file.
 #
-# @filename: the path of a new PPM file to store the image
+# @filename: the path of a new file to store the image
 #
 # @device: ID of the display device that should be dumped. If this parameter
 #          is missing, the primary display will be used. (Since 2.12)
@@ -87,6 +102,9 @@
 #        parameter is missing, head #0 will be used. Also note that the head
 #        can only be specified in conjunction with the device ID. (Since 2.12)
 #
+# @format: image format for screendump is specified. Currently only PNG and
+#             PPM are supported.
+#
 # Returns: Nothing on success
 #
 # Since: 0.14
@@ -99,7 +117,7 @@
 #
 ##
 { 'command': 'screendump',
-  'data': {'filename': 'str', '*device': 'str', '*head': 'int'},
+  'data': {'filename': 'str', '*device': 'str', '*head': 'int', '*format': 
'ImageFormat'},
   'coroutine': true }
 
 ##
diff --git a/ui/console.c b/ui/console.c
index 40eebb6d2c..911092c908 100644
--- a/ui/console.c
+++ b/ui/console.c
@@ -37,6 +37,9 @@
 #include "exec/memory.h"
 #include "io/channel-file.h"
 #include "qom/object.h"
+#ifdef CONFIG_PNG
+#include "png.h"
+#endif
 
 #define DEFAULT_BACKSCROLL 512
 #define CONSOLE_CURSOR_PERIOD 500
@@ -289,6 +292,84 @@ void graphic_hw_invalidate(QemuConsole *con)
     }
 }
 
+#ifdef CONFIG_PNG
+/**
+ * png_save: Take a screenshot as PNG
+ *
+ * Saves screendump as a PNG file
+ *
+ * Returns true for success or false for error.
+ *
+ * @fd: File descriptor for PNG file.
+ * @image: Image data in pixman format.
+ * @errp: Pointer to an error.
+ */
+static bool png_save(int fd, pixman_image_t *image, Error **errp)
+{
+    int width = pixman_image_get_width(image);
+    int height = pixman_image_get_height(image);
+    png_structp png_ptr;
+    png_infop info_ptr;
+    g_autoptr(pixman_image_t) linebuf =
+                            qemu_pixman_linebuf_create(PIXMAN_a8r8g8b8, width);
+    uint8_t *buf = (uint8_t *)pixman_image_get_data(linebuf);
+    FILE *f = fdopen(fd, "wb");
+    int y;
+    if (!f) {
+        error_setg(errp, "Failed to create file from file descriptor");
+        return false;
+    }
+
+    png_ptr = png_create_write_struct(PNG_LIBPNG_VER_STRING, NULL,
+                                           NULL, NULL);
+    if (!png_ptr) {
+        error_setg(errp, "PNG creation failed. Unable to write struct");
+        return false;
+    }
+
+    info_ptr = png_create_info_struct(png_ptr);
+
+    if (!info_ptr) {
+        error_setg(errp, "PNG creation failed. Unable to write info");
+        return false;
+    }
+
+    png_init_io(png_ptr, f);
+
+    png_set_IHDR(png_ptr, info_ptr, width, height, 8,
+                 PNG_COLOR_TYPE_RGB_ALPHA, PNG_INTERLACE_NONE,
+                 PNG_COMPRESSION_TYPE_BASE, PNG_FILTER_TYPE_BASE);
+
+    png_write_info(png_ptr, info_ptr);
+
+    for (y = 0; y < height; ++y) {
+        qemu_pixman_linebuf_fill(linebuf, image, width, 0, y);
+        png_write_row(png_ptr, buf);
+    }
+    qemu_pixman_image_unref(linebuf);
+
+    png_write_end(png_ptr, NULL);
+
+    png_destroy_write_struct(&png_ptr, &info_ptr);
+
+    if (fclose(f) != 0) {
+        error_setg(errp, "PNG creation failed. Unable to close file");
+        return false;
+    }
+
+    return true;
+}
+
+#else /* no png support */
+
+static bool png_save(int fd, pixman_image_t *image, Error **errp)
+{
+    error_setg(errp, "Enable PNG support with libpng for screendump");
+    return false;
+}
+
+#endif /* CONFIG_PNG */
+
 static bool ppm_save(int fd, pixman_image_t *image, Error **errp)
 {
     int width = pixman_image_get_width(image);
@@ -327,7 +408,8 @@ static void graphic_hw_update_bh(void *con)
 /* Safety: coroutine-only, concurrent-coroutine safe, main thread only */
 void coroutine_fn
 qmp_screendump(const char *filename, bool has_device, const char *device,
-               bool has_head, int64_t head, Error **errp)
+               bool has_head, int64_t head, bool has_format,
+               ImageFormat format, Error **errp)
 {
     g_autoptr(pixman_image_t) image = NULL;
     QemuConsole *con;
@@ -383,8 +465,17 @@ qmp_screendump(const char *filename, bool has_device, 
const char *device,
      * yields and releases the BQL. It could produce corrupted dump, but
      * it should be otherwise safe.
      */
-    if (!ppm_save(fd, image, errp)) {
-        qemu_unlink(filename);
+
+    if (has_format && format == IMAGE_FORMAT_PNG) {
+        /* PNG format specified for screendump */
+        if (!png_save(fd, image, errp)) {
+            qemu_unlink(filename);
+        }
+    } else {
+        /* PPM format specified/default for screendump */
+        if (!ppm_save(fd, image, errp)) {
+            qemu_unlink(filename);
+        }
     }
 }
 
-- 
2.22.3