connector/matrix: check the telegram image size limits

Signed-off-by: Sumner Evans <sumner.evans@automattic.com>

pkg/connector/config.go

@@ -48,7 +48,6 @@ type TelegramConfig struct {
 	DeviceInfo DeviceInfo `yaml:"device_info"`
 
 	AnimatedSticker   media.AnimatedStickerConfig `yaml:"animated_sticker"`
-	ImageAsFileSize   int                         `yaml:"image_as_file_size"`
 	ImageAsFilePixels int                         `yaml:"image_as_file_pixels"`
 
 	DisableViewOnce     bool `yaml:"disable_view_once"`
@@ -96,7 +95,6 @@ func upgradeConfig(helper up.Helper) {
 	helper.Copy(up.Int, "animated_sticker", "args", "width")
 	helper.Copy(up.Int, "animated_sticker", "args", "height")
 	helper.Copy(up.Int, "animated_sticker", "args", "fps")
-	helper.Copy(up.Int, "image_as_file_size")
 	helper.Copy(up.Int, "image_as_file_pixels")
 	helper.Copy(up.Bool, "disable_view_once")
 	helper.Copy(up.Bool, "disable_disappearing")

pkg/connector/example-config.yaml

@@ -30,8 +30,6 @@ animated_sticker:
         height: 256
         fps: 25 # only for webm, webp and gif (2, 5, 10, 20 or 25 recommended)
 
-# Maximum size of image in megabytes before sending to Telegram as a document.
-image_as_file_size: 10
 # Maximum number of pixels in an image before sending to Telegram as a
 # document. Defaults to 4096x4096 = 16777216.
 image_as_file_pixels: 16777216

pkg/connector/matrix.go

@@ -64,8 +64,20 @@ func (t *TelegramClient) transferMediaToTelegram(ctx context.Context, content *e
 				return err
 			}
 
+			// Telegram restricts photos in the following ways according to:
+			// https://core.telegram.org/tdlib/docs/classtd_1_1td__api_1_1input_message_photo.html#ae1229ec5026a0b29dc398d87211bf572
+			//
+			// * The photo must be at most 10 MB in size.
+			// * The photo's width and height must not exceed 10,000 in total
+			// * Width and height ratio must be at most 20.
+			//
+			// We also have the image_as_file_pixels configuration threshold to
+			// prevent Telegram from compressing the file.
+			aspectRatio := float64(max(cfg.Height, cfg.Width)) / float64(min(cfg.Height, cfg.Width))
 			forceDocument = cfg.Height*cfg.Width > t.main.Config.ImageAsFilePixels ||
-				info.Size() > int64(t.main.Config.ImageAsFileSize*1024*1024)
+				info.Size() > int64(10*1024*1024) ||
+				aspectRatio > 20 ||
+				cfg.Height+cfg.Width > 10000
 		}
 
 		uploader := uploader.NewUploader(t.client.API())