Re: [PATCH 2/2] Added parameter to take screenshot with screendump as PNG

[Kshitij Suri <kshitij.suri@nutanix.com>]

On 26/02/22 12:37 am, Eric Blake wrote:
> On Fri, Feb 25, 2022 at 11:58:30AM +0000, Kshitij Suri wrote:
>> 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://urldefense.proofpoint.com/v2/url?u=https-3A__gitlab.com_qemu-2Dproject_qemu_-2D_issues_718&d=DwIBAg&c=s883GpUCOChKOHiocYtGcg&r=utjv19Ej9Fb0TB7_DX0o3faQ-OAm2ypPniPyqVSoj_w&m=N58ni_R8AQHe3XV2MX9aeKN2mCiEkpdyiqhV71sHDUEIuIk3P1HcXc-QfepnNaIE&s=CM400Sor3Oiio6iq3V_F9jFMCrn8UdbeKKXDnIh2QRw&e=
>>
>> Signed-off-by: Kshitij Suri <kshitij.suri@nutanix.com>
>> ---
>> +        .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*.
> Maybe:
>
> as an image *filename*, with default format of PPM.
>
>>   ERST
>>   
>>       {
>> 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;
>> +    }
> Instead of open-coding the string-to-enum translation (which will be
> hard to located if we expand to a third format down the road), you
> should use qapi_enum_parse(&ImageFormat_lookup, ...).
>
>> +++ 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 +292,87 @@ 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);
>> +    g_autofree png_struct *png_ptr = NULL;
>> +    g_autofree png_info *info_ptr = NULL;
>> +    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");
> error_setg_errno() might be nicer to use here, since fdopen() failure sets errno.
>
>> +        return false;
>> +    }
>> +
>> +    png_ptr = png_create_write_struct(PNG_LIBPNG_VER_STRING, NULL,
>> +                                           NULL, NULL);
> Indentation looks off.
>
>> +    if (!png_ptr) {
>> +        error_setg(errp, "PNG creation failed. Unable to write struct");
>> +        free(f);
> free() is the wrong function to call on FILE*.  You meant fclose().
Apologies for this, will be replaced in the upcoming patch.
>
>> +        return false;
>> +    }
>> +
>> +    info_ptr = png_create_info_struct(png_ptr);
>> +
>> +    if (!info_ptr) {
>> +        error_setg(errp, "PNG creation failed. Unable to write info");
>> +        free(f);
> and again
>
>> +        png_destroy_write_struct(&png_ptr, &info_ptr);
>> +        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");
> Another spot for error_setg_errno

Thank you for your response! Will send the updated patch out soon.


Regards,

Kshitij

>